Wondering why all plugins for multiple versions put each version in a separate folder giving the customer an extra step to get to the file to upload. Naming the zip file with nopversion would work and would not require these extra folders.
Because a properly structured .zip package with a uploadedItems.json will automatically install the correct version. I.e. your client does not need to extract anything; use the "Upload plugin..." button on the Local plugins page and Choose the .zip file.