I agree that it can be done. I am asking what about it, there will still be the open version. People need to massively migrate to the closed platform, for that to be a problem.
Discussion
All it takes is some company like Tinder to call them out on it, as there will be millions of new users who have no idea they are using Nostr in a proprietary environment.
If they will not know they are using nostr, then they will not use nostr. Thoose who will stay on Nostr the network will propagate the idea of Nostr. The millions on the tinder clone will be shitcoiners and they will be the tinder social network, not on the nostr, even though technicaly they will be. The scenario that you are describing is widening the network of tinder. It is not widening the network of Nostr.