i whole heartedly agree with this.
i've only ever had two actual orgasms from being fucked (i.e., that involved ejaculation), and both were mind blowing incredible. One to the things that stands out to me was how surprised i was (shocked really) when it started happening. The complete and utter loss of control, or really the incredible effect of the Top having that kind of control, for me, is the mattress biting, "You own me" kinda feeling that cuts to the core of me.
i'm not sure i have had the official "assgasm?" Either that, or o have them all of the time. i get knock down, satisfying pleasure from getting fucked. The word "satisfying" feels to weak to me. i don't quite go into refractory like with a penis orgasm, but i have found i can go a long time without an ejaculation when i am being fucked and bred often, especially if it's the same Guy. So, for me it's a definite combination of mental and physical. For several years now, seems i always achieve that state, both physically and mentally, when i get fucked.