Replacing the piston arm using /setblock causes the piston to break (and drop)

I'm not quite sure if this is intended or not, but if you use /setblock to replace a piston arm with something else, the piston would break, like if you would've broken the arm normally

This would make sense, so you wouldn't have a headless piston, but I don't see why the block would drop, instead of just disappearing.

What I expected to happen was:

• When the piston arm gets deleted, the piston gets deleted with it

What actually happened was:

• When the piston arm gets deleted, the piston breaks, making the piston drop

Steps to reproduce:

1. Recreate the setup used in the video

2. Type setblock ~ ~2 ~ air into the command block

3. Press the button

Notice that the piston dropped, instead of just disappearing