You will receive a warning email after you send the app for Apple approval. It is not enough just to add it to the TestFlight. I'm testing the status by submitting to app review (with manual release) and then, once I get a warning email I cancel the release. Email is pretty quick. I would say no more than 15-30 minutes.

I can confirm that the same is happening for me on iOS 15.4.1, Phone 13 Pro.