I frequently get this behaviour on my iPad Pro 12.9“ 3rd gen.
A couple of really, really, annoying examples:
Apollo, the Reddit Client - often, scrolling through a lengthy subreddit for several minutes, I leave the iPad for a few minutes (so it locks the screen) I unlock, and Apollo has been purged from memory completely. Note, in this scenario, I don’t minimise the app...I just leave the iPad, and it still kills it.
Similar behaviour with other apps that you’d use for longer periods of time, for example, Drivetribe, Tapatalk, and Pinterest. And also Safari, and most apps are completely killed if you so much as dare to open the camera, even by accident.
This behaviour was never a thing in iOS 12. it’s gotten considerably worse since iOS 13 and the multiple updates to the new iPadOS have made no difference. Either the new iPadOS actually needs more memory than the iPad Pro has, or they’ve done a horrible job trying to optimise the new operating system.
iPad Pro is supposed to be a professional-level product and iPadOS is supposed to be a capable multitasking operating system. With these significant issues with iPadOS pretty much ruining the user experience, it’s clear that unless this new behaviour is „by design“ (and that is idiotic, if so) then Apple have some significant work to do, to address these problems.
And given their inability to fix some of the widely reported issues with email in iOS 13, I am not holding my breath!