I agree with you OracleDoc but try to create a view(v2)in U2 schema using a U1 tab (U2 view : select * from u1.t1).

U2 can do : select * from u1.t1
U2 CANNOT do : select * from u2.v2 (you need an explicit privilege on u1.t1 ...).

Try this and let me know if I am wrong ?