On my bedrock realms server, I've had mobs drop protection 4 diamond helmets and chestplates with the Flow trim recently in Ominous Trial Chambers, but I don't believe they're supposed to drop them.  I've collected 4 of each in diamond (all prot 4, different damage levels) over the last 3 ominous trial chambers I've visited.  It's seemed to be skeletons dropping them most often in my experience, but that could just be chance.  I don't think we've had them drop on the trial chambers that came out before the creaking update, and we've done like 5 ominous trial chambers before that update.

Possibly related, I did actually find a 3/4-full diamond armor zombie in the wild recently, and it actually dropped all 3 pieces of (unenchanted) armor on death.  I know this is technically possible, but it's VERY unlikely to happen, even though I had looting 3 on my sword.