Using the "Restore iPhone" feature from iTunes/Finder DOES also erase data on the phone, and in fact it's a more radical operation.
Doing "Erase and reset" on the phone leaves the system as-is, only deleting user data; the actual OS remains in place. It's like taking your stuff off the furniture: the furniture remains but everything that belonged to you gets cleaned up.
"Restore iPhone" from iTunes/Finder does that, and also re-installs iOS from scratch. It's akin to emptying the room and bringing new, fresh-from-the-factory furniture in. Even if it looks exactly like it was before, it's new. That's why 1) it takes much longer, 2) it's safer. If your problem were due to, say, a messed up system file, this should fix it.
The only thing deeper than running "Restore" from iTunes/Finder is doing so after putting the phone in DFU mode. That's "Device Firmware Update" and it reinstalls even the firmware, which is the low-level code that sits between iOS and the hardware (technically there's also the bootloader but that's irrelevant as it generally can't be overwritten). That's a last-resort thing to do if the phone is seriously messed up, such as if it doesn't boot properly or it exhibits weird hardware issues. That's way beyond what we're dealing with here.
After resetting or restoring the phone, the "restore backup" phase copies the user data onto the phone or watch, be it from a local backup or from iCloud. That includes the "documents" that each app has saved, such as the images for Photos.app, the health data for Health.app, the saves for games, the settings for apps, etc. It also includes a list of apps, but not the actual app themselves. That's why even restoring from a local backup takes ages after it's done, because it has to redownload the apps from the App Store. That's another step that ensure that the apps themselves are sane.
The reason I'm writing all this is to point out that, depending on the issue, a restore from backup may or may not lead to a fix.
A couple of years ago the heart rate monitor in the workout app of my Series 4 got stuck at 108 bpm. No matter what I did, it would immediately show up 108 bpm and not show anything else. Switching to Heart app would show the correct rate, but Workout always showed 108. I assume (again: I'm not an Apple engineer, but I'm a developer) that the Workout app saves the current bpm somewhere when you change apps, so that it can quickly retrieve that when you go back to it, and show you a temporarily stale rate while it calculates the current one. Had it been possible to uninstall and reinstall the Workout app alone, I'm sure that it would have fixed the problem, but it wasn't (and isn't). So I unpaired the watch and paired it back, restoring from the backup it had just created, and the problem went away. That's because all the "cached" data was cleaned, and there was nothing wrong in the backup itself to trigger it again.
The fact that different people have different rates of success (and different symptoms of the problem to begin with) suggests that there are multiple potential situations. Some only have messed up cached data, so a restore or reset is enough to make things work again. Others, like me, probably have a Health database that's in a worse (or just different) condition, and it takes an actual update to the Health app, or more specifically to the HealthKit framework, to address whichever weird condition it's in. There's also something in between: I still haven't fixed the issue of missing maps, chart gaps and whatnot, but restoring the phone and watch at least prevented the healthkit from reaching 100% cpu and burnin through dozens of percentage points of battery. That's probably because the health database that I restored from my backup is messed up enough to cause glitches, but not to the point of hitting some unaccounted-for condition that just leads the cpu into an infinite loop.
Personally, I'll just wait for Apple to release an update that addresses this. Restoring from a backup takes way too much time, and still requires reconfiguring Apple Pay and other things, so I'd rather avoid dealing with that mess again, especially as I doubt it will change anything in my specific case.
However, I am confident that Apple will release an update for this, be it another 14.0.2 patch, or 14.2 when it's released after the new phones are introduced. There are too many of us for this Health/Fitness issue to be ignored, especially as it's been mentioned on several big Mac-related sites, and given how aggressively Apple promotes the health-related ecosystem of its products.
Wow, I wrote more than I meant to. Well, I hope at least someone found this post vaguely interesting. :-)