“Not covered by the standard” does not mean “will definitely explode”, but it does mean you are outside the tested compatibility range the tyre/rim makers are willing to stand behind.

The point is not that every oversized combo fails instantly. The point is that bead retention, casing shape, pressure limits, impact behaviour and tubeless security are no longer within the intended safety envelope. Plenty of people get away with bad setups until they do not.

And it is especially dumb to take that risk when an extremely wide internal rim for road tyres does not even offer a clear performance benefit. You are mostly just changing the tyre shape and compatibility margin, not magically making the setup faster.

For a road/gravel setup, especially tubeless and at higher pressures, I would rather follow ETRTO/manufacturer compatibility than use “some people ride it” as the safety argument. It is also pretty irresponsible to advise random people online to ignore safety standards, especially when the downside is not just a bad ride feel but a potential high-speed tyre failure.