I recently updated my plugin, both for Studio 2017 and 2019. To avoid a mix-up during upload (and possibly at a consumer's end) I appended to the name of my installers (*.sdlplugin) "2017" and "2019" respectively. ** I did NOT rename the plugin withing the installer itself **.
During the verification process at SDL the line "make sure you completely uninstall the old one using the plugin manager before installing this version as the internal plugin name has changed" was added to my description. I wonder if this is neccessary.
When I run the installation on my PCs (double click on the installer file) the old installation (name without the addition of 2017 / 2019) get correctly overwritten. Thus, the installer file is not itself simply copied do the %appdata%\SDL\SDL Trados Studio\14\Plugins folder but renamed according to the specification within the installer (pluginpackage.manifest.xml).
I think the above warning is only warranted for users with intricate knowledge who might copy the installer manually to the Plugins folder (I'm guessing here, but is this the process at SDL?)