For what it's worth, the Type-M grip frame is measurably thinner than the standard frame. I just searched another forum where I thought I'd posted a photo with a micrometer taking comparative measurements, but couldn't find it...
Suffice it to say that the frame is thinner, and with the thin rubber grip panels (from Farrar, for example), there is a noticeable difference in thickness in the hand. It makes a significant difference for my wife's small hands, and even more so with a short-reach trigger.