I dont think thats true, some are definitely base stations. You can get ones that use your home internet as the backbone. I'll try find one.
Edit: https://en.m.wikipedia.org/wiki/Femtocell
Furthermore, femtocells lower contention on the main network cells, by forming a connection from the end user, through an internet connection, to the operator's private network infrastructure elsewhere.
Dunno if these things are still a thing or not, but it sounds like it would show up as a cell tower.