Anyone who needs any sort of check in or permission seeking before they act on their feelings gets instant rejection from me. I'm not interested in anyone who cannot kiss who and when they want, fuck when they want and has partners with agency over their relationship.
Even when people who have those rules claim there are no veto rights, they aren't being truthful. What will happen is that one or more existing partners will make it so very difficult for them to keep seeing you that they might as well of just said that they are pulling a veto. Please believe me, anyone that is in a poly relationship but has to seek approval, permission or blessing from an existing partner to proceed with a relationship should be treated with extreme caution.