Client isolation is done at L2. You can't add exceptions for IP ranges / protocols / etc this way because that's up the stack. Even if devices can learn about each other in other ways, isolation gets in the way of direct communication between them.

The paper makes the point that you need to consider L3 in client isolation too - they call this the gateway bouncing attack. If you can hairpin traffic for clients at L3, it doesn't matter what preventions you have at L2