This issue prevents MC-148057 to be fully fixed. Banners worn and dropped by captains correctly hide the pattern list, but this property is lost once the banners are placed, mined and picked up in the inventory again. This also prevents banners generated in outposts to hide the pattern list once mined and obtained in the inventory.
To reproduce:
Locate a pillager outpost
Kill a pillager captain and collect the ominous banner
The pattern list won't be shown in the inventory
Place the ominous banner
Mine it
The pattern list will be shown in the inventory
In 20w29a