Using Alex's suggestion, I was able to revert Revit to its original version and then I was able to successfully apply the 2019.2 Update. While testing this behavior, I found that you must run the MSIPATCHREMOVE process for the most recently installed Revit update. To clarify, if the last update applied was the 2019.0.2 Security Fix, then I had to run the MSIPATCHREMOVE process specific to that update but if the 2019.2 Update was applied after the 2019.0.2 Security Fix, then I had to run the MSIPATCHREMOVE process for the 2019.2 Update.
For those of you that want to try this solution, I would recommend running each of the following at a "run as administrator" command prompt:
Msiexec /I {7346B4A0-1900-0510-0000-705C0D862004} MSIPATCHREMOVE={9CA05B9A-1907-0510-A1B4-FFF7A680FE55}
Msiexec /I {7346B4A0-1900-0510-0000-705C0D862004} MSIPATCHREMOVE={9CA05B9A-1905-0510-A1B4-FFF7A680FE55}
Msiexec /I {7346B4A0-1900-0510-0000-705C0D862004} MSIPATCHREMOVE={9CA05B9A-1904-0510-A1B4-FFF7A680FE55}
If a Windows Installer message is displayed stating "The patch is not applied to this product.", you are safe to move along to the next one. When you run the MSIPATCHREMOVE process for the currently applied patch, the process should take a while to complete and will most likely prompt you for the original installation media. When complete, the Revit installation files should be reverted to their original version. Checking the version of the Revit.exe file is a quick method to confirm this change.
At this point, I would recommend running the 2019.2 Update once again. If this action results in a prompt to uninstall or modify this update, select the uninstall option. Once that action is complete, run the 2019.2 Update once again and it should install successfully.
If this approach does not work on your system, the only other workaround is to uninstall and reinstall Revit, then apply the 2019.2 Update. In this scenario, please note that you do not need to uninstall other Revit components, such as the Revit Content Libraries or add-ons (Batch Print or Model Review).
Tony Michniewicz
Revit Software QA Analyst