Hi Clint!
I can say that it works fine, at least in my 8.5 environment where I have non-admin user logged in on managed client computer Windows 7 and after click on "Start Update Installation" from SMA GUI of "Software Updates" tab, Bulletins "VMWT-028" & "MS19-09-IE-4516046" were successfully installed.
Of course if you have enabled 'Allow user to run' in "Default Software Update Plug-in" policy
After mentioned above updates installation, SMA offered to postpone or reboot client computer now, so non-admin user can postpone reboot or start reboot now.
Regards,
IP.