No it’s not.
Every app you launch stays forever stacked in the app switcher —- FOREVER. Years can pass and every app you’ve ever launched that’s still installed will clutter the app switcher no matter how many times the phone is rebooted.
Eventually- you’ll launch every app you’ve got some time or another, maybe months apart - and they’ll all clutter up the app switcher FOREVER unless you clear them out.
So — eventually — if you let iOS do its thing on its own, the app switcher will inevitably stack every app installed in its house of cards, making it almost worthless to use as an app switcher.
The primary reason the powers that be recommend not force quitting apps is to save battery life since they’ll launch from cache, not off the SSD, but if the phone is plugged in, who cares?
What is the problem that "every app you launch stays forever in the app switcher"? Do you suspect a modern iPhone can't handle a list with that much data and that many screenshots? I don't see apps 10 or more down in the app switcher as a problem that needs solution. Also: if you delete an app it won't be in the app switcher anymore.
The total # apps in app switcher cannot exceed the # of apps installed on you iPhone. The space taken up by each app itself (plus its data) FAR exceeds storage space required in the app switcher.
The app switcher isn't "useless" because you can't reasonably scroll through all the apps you've ever opened. Its purpose is to let you quickly switch between recent apps under the theory that, if it wasn't recently open, you're less likely to need it soon.
A big reason to not force quit apps is the same as on a Mac or PC, your kicking the app out of memory and it may not save it's state in an optimal way. The risk of loosing some data is >0, even if the data may not be relevant. This is the very reason that force-quitting a mal-behaving app (frozen, running wildly, etc) is because of this force-quit behavior. iOS apps are generally robust enough force-quit without much issue. And yes, when you re-open the app it will have to load its state from scratch. That consumes more processor cycles/battery and probably RAM than leaving it in the app switcher for sure.
And no, the App Switcher is not a cache. It's a list. iOS saves that "state" of application to storage ("the SSD" as you call it) automatically. The app might prompt iOS to do it, or iOS will do it before it kicks the app out of RAM to use the RAM for something else. Depending on you iPhone model and the apps you run, you will only have a few applications fully loaded in RAM. App Switcher doesn't tell you anything about whether an app is in RAM. (Aside from the last few apps are more likely to be in RAM)
So when you clear apps out of the app switcher, (unless an app is causing trouble) you're really just managing your own happiness a long list of apps, not improving the running of your iPhone. To each his/her own.
PS: apologies for dragging up distant post... my page didn't update and didn't see the multiple new pages in this thread!