It’s obviously a bug caused by fresh code change. Previously same setup worked just fine.
What caused bug?
Default Value that doesn’t exist among Choice values passes Form Required logic.
I have last input value stored in user profile. It is set as Default Value for Choice component that is filled with items from related table. Quite often, previous Choice component filters items so Default Value doesn’t exist. Previously “*Required” worked fine in this situation, but now Submit button becomes allowed and user can submit form without this required column.