I’m afraid I still can't find how you set the patch version in the Control Panel → "Uninstall an update" section. After some research on the internet, apparently only Microsoft knows how to set those fields (Version and Publisher details) for Patches.
However, I think a solution for your problem could be to manually set the patch version into the name of the patch, like most of the vendors do the same for their updates.
As I can see in my Control Panel, even Microsoft uses the version in the patch name for some updates.
In the below screenshot you can see how I added the version for the “Test” patch:
You can set this in the patch project --> "Add/Remove (Control Panel)" --> "Display Patch name".
But, when uninstalling the patch the version downgrade is done, but the software itself does not revert back to the previous version, as expected.
As for this problem, I've tested your scenario, but I cannot reproduce the behavior.
When I uninstall the last patch, the application version reverts as expected to the previous patch version. In the below screenshot is the result after I uninstall de patch 2 update:
Attached are my sample projects (Test 21.0.1.aip, Test 188.8.131.52.aip, Test 184.108.40.206.aip and the two patches). Can you please test them and let me know if they work as expected on your machine? You only have to add an empty "test.txt" file in the "Files and Folders" page.