On iOS by default modals show up in full-screen mode. This behavior can be customized and instead of mouting new screens in top level window they can be mounted under a given UINavController. We used to be relying on that behavior (see "CurrentContext" presentation mode). This, apparently wasn't matching the default functionality of the OS. This change is adding it as a default and keeping the old way under newly exposed presentation modes: containedModal and containedTransparentModal
Thanks to this change, iOS 13 modals can work properly.