Whatever the intent, most people for the time being will be using WP as they’re looking to switch from WC to CC.
It’ll be useful to create some form of compatibility or a migration path so that those people can use your plugin with WP, at least temporarily.
If you’re lucky they’ll also switch to ClassicPress along the line.
So yes, for the time being I’m using Wordpress, and i need the variable thing (or in my case, specifically the virtual and downloadable checboxes that come with it) to work or I can’t switch to either CC or CP.
As this is a common/basic feature in WC, I’m sure most will people will have this simple requirement.