Thanks for reaching out. What do you see under Profile > View and Profile > Edit?
bbpnns-digests comes with support for bbPress out of the box. This means that if you go to the bbPress user screen, you’ll be able to view and edit the options. What BuddyPress does is hijack the bbPress screen and replace it with its own. The options that would show up under bbPress (that the opt-out plugin hooks to) is then shown under Subscriptions (as your screenshot shows).
In order for the user to be able to update the options, I had to write a bridge plugin to make all my bbPress add-ons work nicely with BuddyPress. As an added bonus, the bridge also adds Groups compliance to the add-ons (so that only people of a given group will receive notifications from that group’s forum).
Please provide screenshots of your Profile > View and Profile > Edit screens so I can confirm that this is the case.