Changing the folder does not append “/SketchUp” or similar to the end of the folder path
This causes your software to be installed in unexpected folders, such as the root folder of the folder containing all someone’s software.
Uninstalling your software does not remove only your files. It deletes the entire folder, and any files deleted in this way cannot be recovered.
I strongly suggest you fix this before anyone else loses important software by uninstalling yours.
What version of SketchUp are you talking about? Your profile indicates you are using Sketchup Free (web) which does not get installed on your computer. If you are using SketchUp Pro, please correct your profile.
If you install Sketchup Pro the way it is supposed to be installed, there will be no problems. Your own files will not be touched if you uninstall Sketchup later. Your own files will be saved in a different location than the program files are.
The thing about not appending /SketchUp does seem to be true, and has been reported before. A common variation is where someone decides to install to their desktop, and then they are swamped by SketchUp files all over their nice clean desktop.
Can you say what is your reason for not using the default install location?
The uninstaller does remove the whole Program Files/SketchUp/SketchUp 2021 folder. Can you say why it is you would be going into that folder to add custom files?
I did do a test once where I installed onto the desktop, then ran the uninstaller. It did only remove SketchUp files from the desktop, and not every file.