The answer is not very scholarly, but at least according to the specification in RFC 4960, SCTP seems capable of circumventing head-of-line blocking. The relevant claim seems to be in Section 7.1.
Note: TCP guarantees in-sequence delivery of data to its upper-layer protocol within a single TCP session. This means that when TCP notices a gap in the received sequence number, it waits until the gap is filled before delivering the data that was received with sequence numbers higher than that of the missing data. On the other hand, SCTP can deliver data to its upper-layer protocol even if there is a gap in TSN if the Stream Sequence Numbers are in sequence for a particular stream (i.e., the missing DATA chunks are for a different stream) or if unordered delivery is indicated. Although this does not affect cwnd, it might affect rwnd calculation.
A dilemma is what does "are in sequence for a particular stream" entail? There is some stipulation about delaying delivery to the upper layer until packages are reordered (see Section 6.6, below), but reordering doesn't seem to be conditioned by filling the gaps at the level of the association. Also note the mention in Section 6.2 on the complex distinction between ACK and delivery to the ULP (Upper Layer Protocol).
Whether other stipulations of the RFC indirectly result in the occurence of HOL, and whether it is effective in real-life implementations and situations - these questions warrant further investigation.
Below are some of the excerpts which I've come across in the RFC and which may be relevant.
RFC 4960, Section 6.2 Acknowledgement on Reception of DATA Chunks
When the receiver's advertised window is 0, the receiver MUST drop any new incoming DATA chunk with a TSN larger than the largest TSN received so far. If the new incoming DATA chunk holds a TSN value less than the largest TSN received so far, then the receiver SHOULD drop the largest TSN held for reordering and accept the new incoming DATA chunk. In either case, if such a DATA chunk is dropped, the receiver MUST immediately send back a SACK with the current receive window showing only DATA chunks received and accepted so far. The dropped DATA chunk(s) MUST NOT be included in the SACK, as they were not accepted.
Under certain circumstances, the data receiver may need to drop DATA chunks that it has received but hasn't released from its receive buffers (i.e., delivered to the ULP). These DATA chunks may have been acked in Gap Ack Blocks. For example, the data receiver may be holding data in its receive buffers while reassembling a fragmented user message from its peer when it runs out of receive buffer space. It may drop these DATA chunks even though it has acknowledged them in Gap Ack Blocks. If a data receiver drops DATA chunks, it MUST NOT include them in Gap Ack Blocks in subsequent SACKs until they are received again via retransmission. In addition, the endpoint should take into account the dropped data when calculating its a_rwnd.
Circumstances which highlight how senders may receive acknowledgement for chunks which are ultimately not delivered to the ULP (Upper Layer Protocol).Note this applies to chunks with TSN higher than the Cumulative TSN (i.e. from Gap Ack Blocks). This together with unreliability of SACK order represent good reasons for the stipulation in Section 7.1 (see below).
RFC 4960, Section 6.6 Ordered and Unordered Delivery
Within a stream, an endpoint MUST deliver DATA chunks received with the U flag set to 0 to the upper layer according to the order of their Stream Sequence Number. If DATA chunks arrive out of order of their Stream Sequence Number, the endpoint MUST hold the received DATA chunks from delivery to the ULP until they are reordered.
This is the only stipulation on ordered delivery within a stream in this section; seemingly, reordering does not depend on filling the gaps in ACK-ed chunks.
RFC 4960, Section 7.1 SCTP Differences from TCP Congestion Control
Gap Ack Blocks in the SCTP SACK carry the same semantic meaning as the TCP SACK. TCP considers the information carried in the SACK as advisory information only. SCTP considers the information carried in the Gap Ack Blocks in the SACK chunk as advisory. In SCTP, any DATA chunk that has been acknowledged by SACK, including DATA that arrived at the receiving end out of order, is not considered fully delivered until the Cumulative TSN Ack Point passes the TSN of the DATA chunk (i.e., the DATA chunk has been acknowledged by the Cumulative TSN Ack field in the SACK).
This is stated from the perspective of the sending endpoint, and is accurate for the reason emphasized in section 6.6 above.
Note: TCP guarantees in-sequence delivery of data to its upper-layer protocol within a single TCP session. This means that when TCP notices a gap in the received sequence number, it waits until the gap is filled before delivering the data that was received with sequence numbers higher than that of the missing data. On the other hand, SCTP can deliver data to its upper-layer protocol even if there is a gap in TSN if the Stream Sequence Numbers are in sequence for a particular stream (i.e., the missing DATA chunks are for a different stream) or if unordered delivery is indicated. Although this does not affect cwnd, it might affect rwnd calculation.
This seems to be the core answer to what interests you.
In support of this argument, the format of the SCTP SACK chunk as exposed here and here.
