Ok. Given that, I find the design of this setting with toggles confusing and indeterminate.
Is the goal here to enable the possible use case whereby you only want to allow users to communicate with external SfB users, and *not* external Teams users? If so, then a clearer settings design might have been: to use a group of radio buttons, rather than a pair of toggles which conflict.
radio1: allow both SfB and Teams
radio2: allow only SfB
radio3: don't allow extern comm