Well, the FSSP is doing more than merely providing priests where demand is high and supply is present. They are also training those who are already priests of various dioceses or other religious orders. But my point wasn’t that FSSP priests and others trained by them were so plentiful as to render no further need of Latin-mass priests necessary, but that it’s not as simple as merely accommodating SSPX: SSPX wouldn’t accept mere accommodations without additional demands being met. However, if there are further developments where SSPX would now accept such accommodations, great.
I agree, further accommodations would be great and resolve a difficult/confusing situation. Until then, there are certain places the SSPX can go that the FSSP cannot.
Also one of the issues is that the FSSP still have no bishop. If appointed one, this would hopefully ease some of the trepidation the SSPX have.