I've seen far crazier in friends fish tanks. Small uncycled tanks stuffed with huge fish at several times the recommended stocking levels, on which the only maintenance performed is a full tank tear down, soap and water clean out once a year. Crystal clear water, and no visible discomfort to the fish. These tanks have run on average 5-10 years. Usually they lose a few fish in the beginning (while it cycles), then never experience any problems. Their nitrates are insanely high, but ammonia and nitrite are always non-existent.
Right now I've got a 29g barebottom tank with a Rena XP2 on it, housing around 70 cichlids ranging up to 3 inches each. Been trying to get rid of them for a while, and have nowhere else to house them. I do 50% water changes on it between every 2 weeks and a month. For a short time, it also contained a 10" oscar I was temporarily housing while it's owner resealed their leaking fish tank. Never a dead fish (aside from those the oscar claimed), never a problem whatsoever.
Would I recommend doing any of this? No, not if there were better suited options available. But it goes to show that the "your fish are all going to die immediately" mentality toward stocking levels is often more than a bit extreme. It's one thing to say that a fish would do better in more space, quite another to say there's no way it can possibly survive or thrive in said space (within reason of course, I'm looking at you Mr. Oscar in a betta bowl, lol).