Additionally we have observed that willDisplayCell gets called for every cell upon device rotation without any calls to updating the snapshot.

Thank you for your response. But I'm afraid what I'm observing contradicts what you've said. The sample app for Updating Collection Views Using Diffable Data Sources  is already using applySnapshotUsingReloadData and yet willDisplay is called for all cells even those not on-screen. I had to add a number of extra entries into the recipeData.json within that sample project in order to have more cells than can be rendered on-screen. But after doing so and adding a print statement in willDisplay I observed that it was being called for all cells (including those not on-screen). The same is true using for animatingDifferences: false (observed on both iOS 14 and iOS 15). Should I file a bug report if this is not expected behaviour?

No response received on this from Apple, instead we fixed our issue where it was possible to open the company website from within the ASWebAuthenticationSession. Honestly my anecdotal experience so far is that if someone from the App Review team sees the word "Cookies" then they will instantly reject the app without considering context or technology.