Version Discrepancy? Play store v. Settings->Apps->Firefox

On phone1, having issues leading to recurrent OOM crashes (even after reboot & initial app start) that only end with force stop. Investigating that, noticed version discrepancy between play store & system settings (+browser->settings->about on phone2)

Browser [on phone2] says:
“83.1.0 (Build #2015776401)
AC: 63.0.9, fc54c566e
GV: 83.0-20201112153044
AS: 63.0.0
Wednesday 11/18 @ 6:23 PM”

System Settings->Apps->Firefox says 83.1.0
Play store says 82.1.3 updated on Nov 9, 2020

Is this expected? Are there side-loaded updates? Or is something unusual afoot?