In ServiceNow, parent-level wildcard (.*) ACLs apply to all fields on the parent table AND inherited tables (child tables).
Since the user at child-level lacks u_test, they fail the parent wildcard check, denying field access even if the child table has its own CRUD rules.

Possible fix could be

1. Add a child.* ACL //overrides the inherited parent.* restriction for the child table

OR

2. Add u_test1 to the parent.* ACL