I just stumbled upon my own question and saw it unanswered :-) Meanwhile, my girflfriend and I both are playing with a headset of this model. No interference, even in the same room. So no worries, at least this works ;-)

Hei Cynthion

did you test this in the meantime? I can't speak for this logitech headset specificly but about 10 years ago me and my brother had the same logitech wireless headset and we didnt have any interference. But we were playing in different room.
However, no interference occurred when we walked into each others room (airdistance between dongles roughly 3-4 meters).

Not tested myself, but if you are closer than 1m, you potentially run into interference problems.