The backups aren't the problem - what is the problem is Apple's "solution" to a clear bug being "don't restore from backups" (for the cellular-data draining bug).
Instead of asking you to lose all your data as a workaround to a bad bug, they should actually fix that bug properly, so that it's no longer a bug.
Likely the same with the bug described in this story - if someone ends up affected by it, they're basically pooched: they can't do any more new backups, and likely if they do restore from a previous backup where data exists that triggers this, they're just going to get into that same loop of problems.
And because it's not a "high severity" (RCE) bug, it's likely never really going to get fixed as there are "workarounds for it" (read: wipe/setup the device and omit your data) or "other mitigations implemented already (previous versions of the OS be damned!)" as noted in the story.
Backups should be able to be merged with data on the phone. The use case is I want to travel overseas but I don't want various border control entities to make copies of my phone contents, so I back it up and reset the phone to factory defaults. Then I go on my trip and take pictures and receive texts and etc. When I get home I should be able to merge the pre-trip backup and the during trip stuff into a single set of contents on my phone.
iOS backup apparently doesn't work like you described. E.g., when restoring a backup from iOS 14, it doesn't revert your system to iOS 14. Clearly there's a separation of restoring the executables and restoring the configs.
I do expect "the config/setup that would trigger a battery drain in <iOS X" to be restored, but Apple can always fix iOS so that the same config/setup won't break >=iOS X.
Instead of asking you to lose all your data as a workaround to a bad bug, they should actually fix that bug properly, so that it's no longer a bug.
Likely the same with the bug described in this story - if someone ends up affected by it, they're basically pooched: they can't do any more new backups, and likely if they do restore from a previous backup where data exists that triggers this, they're just going to get into that same loop of problems.
And because it's not a "high severity" (RCE) bug, it's likely never really going to get fixed as there are "workarounds for it" (read: wipe/setup the device and omit your data) or "other mitigations implemented already (previous versions of the OS be damned!)" as noted in the story.