The bias that men tend to be physically stronger than women, pound for pound? The 50-100% estimate is probably an exaggeration, but from my quick glance at competitive weightlifting results, 25% seems well-supported.
According to the Wikipedia article of Olympic weightlifting world records, the 69kg men's record total lift is 359kg, while for women that record is 286kg. That's about a 25% difference.
Of course, world records might not be the best thing to look at, since the variance among the genders is probably different (although this discussion is about top MMA fighters, so it's fairly appropriate). Also, you can probably find very different numbers by looking at different weight classes and events.
Just a side note, "175%+" is actually a bit of an underestimate.
As an example, I'm 175# and can bench press 285# (3 whites) but I'm not a "strong male athlete" by any means.
Athletes who train for strength (linemen, powerlifters like GZCL) are putting up 2x their body weight or more, and that's just for bench press alone which is usually the lightest event.
Deadlifts and squats can hit 4x body weight which is just insane.
A strong male athlete can bench press 150%-175%+ his body weight. You think Rousey can do 6 x 240 pounds? Not a chance.