I have heard that some Buff Orpington Hens are commonly thought to be Roos because they have larger combs... I have seen pics of other peoples buff orpingtons that I would have thought were roos but were actually hens.... that is why I am still not sure. Plus this girl (or guy) was pre-sexed as a pullet. I guess only time will tell. Either way - he/she is very very sweet and affectionate.
We have 4 Buff Orpington pullets that are now 16 weeks old. None of them have combs like that now, and red combs at 10 weeks is another big indicator of roo. I see that the chicken in question is with another..... is his comb more developed and more red than the other? That would be another clue.
Pre-sexed "pullets" end up as roosters with feminine names quite often. We've had some ourselves! lol