The AR doesn't need to have a dust cover, at least according to In Range TV

[Univibe]

The 'scallop' is just as effective for pulling a difficult-to-extract round from the chamber, as for pushing the bolt closed, I reckon.

The scallop is there to operate the dust cover when the bolt moves.

 

[Oldsalt66]

Another thing the forward assist is good for is forcing the next round to feed against a squib that's stuck not too far into the barrel, but just far enough to prevent the next round to chamber properly.

Slam that forward assist to seat the next round behind a squib, and....Kaboom.