I don't know why Microsoft threw all their eggs into the MSI basket
I still had to manually uninstall Office 2013 or Office 2016 on some machines to allow the SCCM install to run properly. If you just want to nuke the exiting MSI install from orbit, the RemoveMSI option does a pretty good job at cleaning up that said, I did have specific scripts to start the Office 2013 or Office 2016 uninstall process set up in SCCM (with detection rules, and obsoletes set up) to clear the way for the Office 2019 C2R setup.
