This is correct, and to understand why - mobile operating systems handle application lifecycles differently than desktop operating systems do.

Desktop operating systems generally leave managing application lifecycles entirely up to the user - you will run out of resources by running too many applications simultaneously.

Mobile operating systems are designed from the ground up to conserve resources given their relatively weaker hardware profiles, and applications in the background will mostly gracefully shut down when other applications need their resources. This means apps that you see in the app switcher are not necessarily actually running any more - they may be dead already and get recreated when you switch to them. If you have a keen eye you can tell when this happens as there will be a longer loading time to open the app as compared to if the app is still alive once switched to.

As a general rule, it's not a good idea to manually close apps on the app switcher, as the apps in a backgrounded state can only be opened faster at no real performance penalty - you're actively making your experience worse by doing this.

The exception (applies for Android only, I can't speak for iOS) is apps that show 'persistent' notifications - these are allowed by the system to perform more significant background work, and as such, you should scrutinize apps that do this more than others.

Apps can still start while being closed on the app switcher so you should still not do this, fwiw.