The best way (currently) to ensure that updates deploy only things you want is to duplicate a block, update it, then check it out. @acjnas is spot on about what updates should do and should not, especially when it comes to performance and bug issues done in the background (instead of in an update). There have been times where I’ve noticed a bug, and instead of reporting it, I updated the block to get rid of it. This fixed the problem, but what if I wanted to keep the previous version of the block?
I brought up a similar topic over a year ago, after finding random blocks that had essentially expired: