If a creeper is killed by a bogged's arrow (or kill credit is given to the bogged in a different way), it will not drop a music disc. The regular skeleton and it's variants (stray and wither skeleton) will cause a music disc to drop.

Steps to reproduce

1. Turn on Update 1.21 experimental toggle
2. Find or spawn a bogged
3. Find or spawn a creeper
4. Go into survival mode
5. Get the bogged to shoot at the creeper while it is trying to hit you (using another mob like the snow golem will not work because of MCPE-178902)
6. Repeat step 5 until creeper is killed. 

Observed Results:

The creeper will not drop a music disc will drop, only gunpowder.

Expected Results

A music disc would be dropped by the creeper along with gunpowder.