I see a hugh difference. If this was reversed and you were dealing with walking or babbling, etc not until age 27 months (not within the normal time frame) that would be view medically as a delay- why isn't this? It is occurring outside of the medium age (at least would normally would have been) be it because of something- is it not?
I don't know, my DS had some social/emotional delays, maybe that is why he trained late, but I'm not sure what to say about his toddler friends who also trained late but have no other delays. I guess I am disagreeing with your average or "normal" age of potty learning. You seem to be saying that the normal age is 12-18mos. I'm saying I feel the normal age is more like 12-36mos. I don't think that this is a big change from years ago, I think it's just more apparent now because coercive & abusive methods are no longer in use -- in other words, I think a lot of trained 18mo kids years ago would not have been trained so early if gentler methods had been used. I also think that no one has properly defined "potty trained" -- does it mean simply out of diapers? Does it mean completely accident-free? Does it mean the child needs no reminders? Does it mean dry at night, too? How can you say kids trained earlier years ago, if we don't have a working definition for "potty trained"?
I don't see why there can't be a large range of readiness... at 2yo, my DS could talk like a 4yo, used scissors and crayons like a 4yo, etc. but that doesn't mean other kids his age were 'behind' because they talked like 2yo's and had more limited fine motor control. There has to be room in developmental milestones for the large range at which kids will meet them, and I believe this applies to pottying too. Maybe years ago, people were ashamed to have a 3yo still in diapers, so they kept quiet about it... who knows??