Why pruned nodes can skip witness downloads for assume-valid blocks
Two years ago I asked in BSE why (segregated) witness data is downloaded for assume-valid blocks in pruned mode. We don't validate these witnesses, and we delete them shortly after. Pieter Wuille explained that skipping witness downloads would require extending the set of consensus checks delegated to assume-valid. But implementing this change is relatively straightforward, and because SegWit witness data now makes up a significant portion of each block, omitting it can cut bandwidth usage by over 40%.