Clarify formSheet flex limitations (#1416)

* clarify formSheet flex limitations note

* apply suggestions from code review

Co-authored-by: Kacper Kafara <[email protected]>

* styling

---------

Co-authored-by: Kacper Kafara <[email protected]>

Author: kligarski

versioned_docs/version-7.x/native-stack-navigator.md

@@ -1038,11 +1038,13 @@ export default function App() {
 
 :::warning
 
-Due to technical issues in platform component integration with `react-native`, `presentation: 'formSheet'` has limited support for `flex: 1`. The tradeoff is necessary to prevent ["sheet flickering" problem on iOS](https://github.com/software-mansion/react-native-screens/issues/1722). Work on the problem is [in progress](https://github.com/software-mansion/react-native-screens/pull/2748).
+Due to technical issues in platform component integration with `react-native`, `presentation: 'formSheet'` has limited support for `flex: 1`.
 
-Currently on Android, using `flex: 1` on a top-level content container passed to a `formSheet` with `showAllowedDetents: 'fitToContents'` causes the sheet to not display at all, leaving only the dimmed background visible.
+On Android, using `flex: 1` on a top-level content container passed to a `formSheet` with `showAllowedDetents: 'fitToContents'` causes the sheet to not display at all, leaving only the dimmed background visible. This is because it is the sheet, not the parent who is source of the size. Setting fixed values for `sheetAllowedDetents`, e.g. `[0.4, 0.9]`, works correctly (content is aligned for the highest detent).
 
-Unfortunately, even if you don't use `flex: 1` but the content's height is less than max screen height, the rest of the sheet might become translucent or use the default theme background color (you can see this happening on the screenshots in the descrption of [this PR](https://github.com/software-mansion/react-native-screens/pull/2462)). To match the sheet to the background of your content, set `backgroundColor` in the `contentStyle` prop of the given screen.
+On iOS, `flex: 1` with `showAllowedDetents: 'fitToContents'` works properly but setting a fixed value for `showAllowedDetents` causes the screen to not respect the `flex: 1` style - the height of the container does not fill the `formSheet` fully, but rather inherits intrinsic size of its contents. This tradeoff is _currently_ necessary to prevent ["sheet flickering" problem on iOS](https://github.com/software-mansion/react-native-screens/issues/1722).
+
+If you don't use `flex: 1` but the content's height is less than max screen height, the rest of the sheet might become translucent or use the default theme background color (you can see this happening on the screenshots in the descrption of [this PR](https://github.com/software-mansion/react-native-screens/pull/2462)). To match the sheet to the background of your content, set `backgroundColor` in the `contentStyle` prop of the given screen.
 
 On Android, there are also some problems with getting nested ScrollViews to work properly. The solution is to set `nestedScrollEnabled` on the `ScrollView`, but this does not work if the content's height is less than the `ScrollView`'s height. Please see [this PR](https://github.com/facebook/react-native/pull/44099) for details and suggested [workaround](https://github.com/facebook/react-native/pull/44099#issuecomment-2058469661).
 :::