> but it seems manipulative to try and make their pricing negotiations a social movement

One restaurant leaving the platform will likely be much worse for that restaurant, but many leaving the scheme will be worse for the platform. No one restaurant has much bargaining power to demand better terms, but many together may be able to bargain better.

It seems to me like this is exactly how they demand better terms and change the balance of power in the relationship.

One could say that the platform putting such strain on the restaurants is manipulative because they know that it's very difficult for any restaurant to say no. I think it's just how the market works and think it's great that the restaurants are managing to push back somewhat.