Pretty sure it only applies to anyone pushing out an update.
There is nothing to stop developers keeping old apps on the app store and not updating them, for whatever reason. If you’ve had a phone or tablet for a few years you probably have some apps that are updated very frequently, some only occasionally, some not at all. And they just keep working.
Even through iOS updates require new versions of the iOS SDK for new apps, old apps generally keep working. There might be a few that require updates, but the majority don’t. Updates that mean all apps older than a certain age need to be updated, like the requirement that all 32 bit apps are updated to 64 bits, are quite rare – in fact I think that’s the only one. And even if an app needs updating to take advantage of an OS or hardware update, it can still be used on millions of older devices and devices running older versions of iOS.