I've used plenty of Mercon-V in Toyota PSFs. No issues. I'd say the fluid looked better and steering worked better, especially in winter, than conventional dex/merc.
Too many clueless in Toyota forums and on the internet. Most Mercon-V's are multispec that includes dex/merc.
Locally available clearance Mobil1 and RoyalPurple ATF are in my 3 Toyota pumps now, after years of various synth PSFs, like Amsoil, Redline, Royalpurple, Lubegard, Bardahl, Prestone, Gunk.... along with synth ATF's including Redline, BG, Valvoline, Pennzoil, Castrol....
I siphon and refill at every oil change interval, grab whatever is on the shelf, and have yet to lose a PS pump or develop any leaks. So, I don't need to pay for some silly shop 'flush' with unknown flush chemicals, additives, or fluids. Same works for my Nissans/HyundaiKias/Mazdas...
There really is no mass incompatibility. But, there are many who want to blame any fluid for their never maintained and/or run dry power steering system(or engine or coolant or transmission or xfercase or diff), that has already failed.