I have a couple of issues with that.
1. Adding another fan, at least a decent one with high static pressure now gets you in the price range of coolers that offer better performance for the same price of the unit plus the added fan.
2. Mismatching fans don't equate to better performance because you you have to balance fan speeds and find that happy medium which results in a max of a few degree difference.
3. Replacing both fans with the best out there "$46 just for the fans" only garners you a max 4°C increase in performance on any 212 unit.
4. Adding a fan with the Rear Exhaust still in place gains you next to nothing.
Basically, the best of the 212 lines in any configuration is still less of a performer than a
MasterAir Pro 4 $40 "$4 more expensive" and you can see how I listed what is better from that point on.
Then you have a one of a kind Chip/Cooler.
When I said this is common, across the 20 initial reviews and countless Reddit threads and even Tom's this is a common complaint. Temps seem better across X570 boards but I believe that has to do with much better optimization around the chip that includes better fan profiles.
I have an X370 myself and with the stock cooler regardless of what I did, it hit 80°C for a few seconds until I used the Wraith Prism. The Prism could keep the temps down under a stress test just fine but it also added an annoying noise that my open-backed headphones seemed to amplify.