Modern Android aggressively kills applications in the background. Android apps have to be designed around this paradigm: That is the app can be killed at any moment when in the background, and must be able to seamlessly restart and pick up where things were left off
OK that makes a certain degree of sense and explains some things I’ve seen.
However–android really ought to remove the thing from the task list if the process has been killed. It certainly gives me the wrong impression as to what is going on. I’m left wondering why, if Firefox has been running, why it has to reload the damned page! (Which is excruciatingly slow 90% of the time.) It’s a lose-lose for Firefox that way (I complain that it won’t quit and I complain that it thinks it has to reload the pages, when in fact it DID quit, which would be a good thing, and therefore MUST reload the page, which is understandable at that point). What makes that even worse is that Firefox is one of the very few things I deliberately leave up, just so this doesn’t have to happen (and yet it does anyway!)
I have no idea if this is feasible, but for Firefox the ideal might be to have it stay resident, but have its access to the antenna be cut off while it is “minimized” (not the top process). That way a page like one on Wikipedia or anything that doesn’t do a lot of donkeying around with constantly hitting the internet to run movies of dancing kittens (or whatever the heck) while just being looked at doesn’t need reloading.