Generally, from my own research and from what models who run an OF and other producers tell, OF customers are mostly a different kind. So its not full canibalisation there OF steals models or customers.
Most OF models would never do porn in the first place. And mayn OF customers just dont find on normal porn sites what they get with OF.
On OF you get personal contact (well often just fake by some OF agency who writes with customers), and just more of THAT ONE MODEL.
Porn sites rather have a broader approach, they deliver different models, differnt scenes. Sometimes locations and stories you wouldnt think of doing as a OF model. If you look to VR content, to str8 porn studios like Vixen or Lustfilms who do even full featured Movies (like real movies with full story).
If i get OF models, that usually by telling them that they can gain more customers by being on a porn site (its a selling channel for them). Mostly they just refuse and most of them with a attitude like "I am a superstar". Well more like a one day fly for me