After updating to 20w28a snapshot existing pillager outposts stop spawning pillagers.

To recreate this do the following:

1. Create/join a world in 20w27a or below.
2. Locate a pillager outpost.
3. Save and quit.
4. Join the world again in 20w28a.
5. Remove the hostile mobs so new ones can spawn. I set the world to peacefull and back to normal difficulty.
   → No new pillagers will spawn at the outpost and the outpost doesn't show up using the /locate command.