[jakobegger]

I wonder if the App Store Review team will check that setting? I've had a Mac App rejected because sandbox restrictions weren't narrow enough.

If it was my decision, I'd allow disabling App Transport Security if your app is something like a browser or an RSS client, were you need to connect to servers not under your control.

If you need to disable it to make ads work, I'd reject it.

[MrGando]

No, they won't be rejecting apps based on that setting. They know this is a progressive measure, and maybe some day in the future they will... but if you watch this year's WWDC session on this topic, it's pretty clear that they won't be rejecting anyone.