Too lazy to read through the whole thread, I may give a statement to the first posting.
I think there is a point in it. Having been a natural 8+” in length and just a bit over 5.5 in girth, but with a 6” glans at full erection, I can confirm that there are potential problems.
Yes, having sex requires with most women more “preparation” - or at least more additional lubrication. And doggy style or any position adept to deep pounding has been initiated with care. I had women who were asking to slam it in on first penetration because they wanted it out of sheer excitement. Several times, I made the error to obey and they regretted it pretty fast (and me too because that ended the joy abruptly). So I got used to make a first ‘test dive’ with ease and only after knowing I did not hit painful spots started to give her powerful thrusts. And yes, this can be irritating because you have to control yourself in moments where self-control is not desirable.
On the other hand, I had a few women who did enjoy the depth and girth of the penetration at first entrance. This is not often the case and extremely lustful, I must admit. And then you and her or him may enjoy the game of “overly long” penetrations, by penetrating extremely slowly, and she/he starts to ask like “is there still more to come?” - and I can confirm. That is a little mind game which can be as exciting as pounding away like an overheated steam engine. But I guess this is less length-related than time-related. Size is NOT everything!
Plus I do like active (and sometimes passive) anal, so girth can be challenging. For those who don’t believe I recommend to try a dildo of the size they dream for their own dick - in their own butt. I did, and believe me, that changes the perspective :-)
And until now, three women were able to deepthroat me - hmmm, now that’s a reason for marriage :-) just joking, but yes my Lady is among them…
On the other hand, having a big one is not a disadvantage too. If it is in a long-term relationship, there are anyway different reasons and, most important, different levels of communication about and during sex. So you work mutually with what you are given, as to say.
I’d say the OP statement is more valid for casual sex, but then I think it is pretty valid.