No, your Android native application will not be affected. The changes described in the email apply only to Web apps, Android has a separate SDK for user sign-in. No changes necessary.

A cached version of your sign-in library that itself depends upon and uses the older, deprecated JS library, or an installed build still in use by older devices which have not updated recently perhaps? Internal test tools that have not been updated, developers testing on their own machines, or sign-in using WebView may also be areas to consider. If possible, instrumenting the places which load api.js/client.js to count the frequency of use may give you hints on whether this is a few internal folks testing or working with older packages, or more seriously a widely deployed production app.