They aren't just reset after every restart / upgrade but even without running any update or restarting.
One problem that results from this beyond having to change the settings after update is that firewall apps can get disabled.
After every update the NetGuard firewall was disabled which may be caused by this or be a separate issue.
Additionally, nonessential things/apps like "Facebook Services" can't be set to "Optimize".
For example, "Analytics" is constantly set back to "Don't Optimize", simply overriding my decision to disable it.
How to persist the battery optimization settings?