Here's one of my 3090's in a test rig with just the default Xintensity:
My results while testing --xintensity 224
crazypool: 0-1% stales
nicehash: 0-1% stales
ethermine: 1-2% stales
flexpool: 2-3% stales
I had to lower the -xxintensity down to 144 to get 0-1% stales on flexpool. So different pools have different optimal intensity settings.
As a miner developer it's hard to set the "correct" one. It require alot of testing.