Execute privilege via role

I can't seem to find a clear answer to this question. I understand definer vs invoker rights with regards to packages/procedures, and the fact that Oracle will ignore roles when determining access to objects used in the procedure. But what about the EXECUTE privilege itself? I'll give you an example:

User A owns tables used in a package that it also owns. The package was created with definer rights.

User B does not have any grants against tables owned by User A, but does have EXECUTE on User A's package.

In this case, User B can execute Users A's package with no issues.