Vindicators riding on ravagers never spawn in raids

Based on the 1.11.0.1 Beta changelog (Which can be seen here), ravagers can be ridden by pillagers and vindicators (and evokers even if not mentioned).

However there were no vindicators spawning on top of any ravager in a raid, making them unused. They can only be spawned via commands such as this:

Command:

 /summon ravager ~ ~ ~ minecraft:spawn_with_vindicator_rider 

How to reproduce

1. Cause a raid
2. Defeat the raid
   → You'll notice that in late waves, no vindicator riders spawn on top of their ravagers.