Its not a bug, but I don't know how to write an issue.
I am not a developer, so write this issue as user. I have a lot of applications which are using Squirrel as installer. The problem for me is the folder naming.
Example:
GitHub desktop (for Windows) has working folder app-3.1.1, but there are old folder app-3.0.1 with files. The application uses files from folder app-3.1.1. So why the old folder still there? Why installer kept it?

Is there any option or switch to remove old installation directories.
And option DON'T USE numbers in folder. Is very difficult to create firewall rules every application update.