As a fellow software maintainer I understand your concerns. I would also be annoyed if lots of users came to me asking for support on an old version of my software with no way to update.
Most plugins on the Minehut panel include the Spigot link so users can easily access it, I've attached a screenshot of your plugin.
Spigot metrics would not be reliable if you want to count the amount of Minehut servers using your plugin. You can use bStats though; my plugin on Minehut uses bStats and it allows me to accurately measure how many servers have the plugin installed.
I believe a plugin author didn't like Minehut using their plugin a while ago and Minehut refused to remove it, but it couldn't hurt to e-mail them and ask if you want your plugin to be removed / changed.