Arguably we should never omit the bloom filter, and even taking a complete shot-in-the-dark random CIDs from your store and sending that across has the potential to avoid round trips. As usual, this is through the filter that "the worst we can do is the same number of round trips as BitSwap". The downside is that this may (with some low probability) prevent a sibling block from being transferred, adding a round trip. From a probability perspective, it probably makes sense to do.
Arguably we should never omit the bloom filter, and even taking a complete shot-in-the-dark random CIDs from your store and sending that across has the potential to avoid round trips. As usual, this is through the filter that "the worst we can do is the same number of round trips as BitSwap". The downside is that this may (with some low probability) prevent a sibling block from being transferred, adding a round trip. From a probability perspective, it probably makes sense to do.