I was able to reach a very kind and helpful customer service rep this morning, and she found essentially the same info I did. The assumption is that conditional call forwarding is not possible on a Pay As You Go phone. There's nothing on Rogers' site that indicates this is a limitation, but there was no way for me or the customer service rep to activate it; all we could activate is the unconditional call forwarding. I have recommended that the "Use Call Forwarding" page and the Pay As You Go pages be updated to reflect this limitation (if the assumption is correct).
For those searching this thread: you can activate unconditional call forwarding via the method on this page:
https://www.rogers.com/customer/support/article/use-wireless-call-forwarding
You may have to go though a series of prompts on *611 to find the switch to activate the Call Forwarding option on your account (as I did) before using the above method.
