Obsevers don't detect block updates, they detect shape updates. This bug is likely unrelated to this change, it happens even if you run redstone directly into the observer, as if you were powering it, which does send block update to the observer.
> In that case it's probably for the best that the change be kept whether accidental or purposeful, since people will soon start building things with the new physics
I disagree, the amount of machines we have now and that were being developed as this change happened is much bigger than what we might develop within a few updates, not to mention that current behaviour just makes less sense, at least in my opinion, with ptojectiles being redirected or stopped by pistons or water.
Sorry, i got the version range wrong, this behaviour starts in 1.20.5. Updated the report
Pretty sure that's WAI. Wither has 1/1000 chance to shoot blue skull instead of black from its main head
I suspect this happens because fireballs explode in position where they last ticked and not directly at point of impact and because they accelerate up to almost 1.9 blocks per tick and their block breaking range is 1.7(3) blocks they can actually colide with a block and explode so that it is outside of explosion range, try moving the wall 1 block further and it should be destroyed again. With wither skulls its the same situation except they accelerate to much higher speeds, maybe even infinite, but the principle is the same.
Note that wind charge explosions not affecting other wind charges is useful and should not be changed, because it allows for cannons that use stacked wind charges as propellant, which would be broken if wind charges started pushing eachother, because the first wind charge to explode would change momentum and therefore explosion location of the following ones, causing unpredictable behaviour. This wouldn’t be an issue if wind charges were only affected by non wind charge explosions.