This is NOT correct.
We can install unpatch Catalina from a VM, or another Mac. Then all we need is just a no compat check boot argument to boot unpatch Catalina on cMP.
Obsolete, please use OpenCore to have native installs of Catalina with MP5,1. https://forums.macrumors.com/threads/opencore-on-the-mac-pro.2207814/
forums.macrumors.com
OpenCore is our recommended method, which can provide boot picker, HWAccel, and allow us to boot to Catalina recovery partition etc. However, never a requirement to install / run vanilla Catalina on cMP.
Since you already have Catalina installed, all you need now is just that boot argument to boot Catalina, and test if tooltips can work properly.