@Jerry hmm. I don't think so, because if it's like a normal activityPub instance, it would honor the block and the boosted post is a direct relay of the post from the original server, so blocks should be honored with boosts.
"Quote posts" however, arent the same and could be relayed to Threads.
Boosts are block protected because of the way it's built into the code as far as I'm aware.🤷♂️