It would be nice to see a well-designed study with lots of different treed saddle, different treeless saddle, different shaped horses AND a wide variety of riders.
Personally, I suspect the biggest contributor to accidents, pressure sores, etc. are riders who can’t really ride very well
Those who don’t have particularly good balance, are overweight and don’t have an “independent” seat.
I suspect that a certain # of treeless supporters (aside from those who jump on any fad) are fairly new riders who are attracted to treeless because of the generally lower cost and the mistake-free idea that it will fit “any” horse.
Makes it as easy as writing a check…
Now, before the mob starts forming and lighting their torches, this is not an all-inclusive statement, but I have seen these people be attracted to treeless for the reasons stated…