> The “Follow” button is visible when I take the screenshot mid-switch.
Does this indicate that the privacy feature has a gap, where you could reveal the length of your password if you take a screenshot mid app switch?
Probably, but to the extent that was at all a problem to begin with, multiply it by another 0.0001 or whatever for the threat of the screenshot being taken mid switch away!
No because per default the input is not cleared when screenshotting. If you‘d implement this yourself for security reasons you'd most likely blur / overlay the whole screen when the app enters background state.