I'd say the vast majority of folding bikes fall into the very general "hybrid" category, with rare outliers in the drop bar road bike or fat tire mtn bike categories.
The term "Hybrid" used to mean something, but has now been further and further split by bike companies into narrower niches designed to appeal to different buyers.
I work in a Trek shop, so while they do have a specific bike line with the title "hybrid," when a customer asks for a hybrid bike, I need to further narrow it down a bit. Could be asking for more a dual sport (DS), fitness bike (FX), hybrid (Verve), or comfort bike (Shift).
So "Folding Bike" is fine because it generally separates them from regular, upright bikes, and because most of them actually do fit into the very general hybrid category.
After than, it's really up to the consumer to examine the finer details and pick one right for them, or ask those in the know for direction and possibilities for their particular needs.