Moving blocks don't drop items

Updated descripton by [Mod] GoldenHelmet

 Steps to reproduce

1. Set a repeating command block with the command /setblock X Y Z <block> destroy
2. Set up a sticky piston attached to a clock circuit so that it repeatedly pulls away then pushes back the the blocks that are set.

Expected results

Each time the block is destroyed by commands, it drops that block and you see particles for that block.

Actual results

Sometimes the block does not drop, and you see update block particles.

Demo using above steps

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Original description
Moving blocks do not drop items when broken by withers or commands. The easiest way to reproduce this bug is to set a repeating command block with the command /fill (x y z)(x y z) air 0 destroy, and then you push blocks with pistons within the region of the fill command.