updates – Is it normal for an Android OS upgrade to change bitness on an upgrade?

I support an android app, that uses native files. (multiple APKs)
Some app setup is done on first startup, (which is different for 32bit + 64bit).

Recently I dealt with a bug report, caused by a users OS being upgraded from Android 7.1 to android 8.1. Surprisingly to me the OS changed from 32bit to 64bit. I don’t have direct contact with the user, so I don’t know if this was the user manually upgrading the OS on a rooted device, or a standard OS upgrade.

Is this a normal thing that can happen for non rooted devices?