Even after reading through the release notes I still don't know if this is intended behavior (and I did search). On 1.14.60 and earlier versions I used to do quite a trade in nuggets by luring armor wearing zombies into deep water and letting then drown. They always dropped all worn and carried items. They no longer do this all of the time, it seems to be about 50-50 now. Zombies wearing armor will convert to drowned and the drowned is still wearing the armor.
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Steps to reproduce
1. Find a zombie spawner
2. Arrange a water trap beneath the spawner to wash zombies into a drop chute to a water filled room (my room is three high and floored in hoppers that direct to a chest, the only source blocks are at ceiling height to insure that falling water washes drops down and they do not float but this is not necessary for the test)
3, Watch for zombies with armor
4. Observe zombies drowning and note the percentage that do not drop worn (or carried) items when they convert to drowned. A number will still be wearing/holding items after converting to drowned.

Drowning zombies do still always drop armor. What is happening is that if they have the ability to pick up items then they immediately pick up and equip armor that they dropped. You can verify that this is what is happening if you closely watch armored zombies when they drown.
If that new-converted drowned cannot pick up items, then another one nearby that has the ability may grab the armor. About 1/4 mobs spawns with the ability to pick up items.
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