The problem I have with all these claims, including yours coming from a person that loves common plecs and has kept so many of them, is that people tend to exaggerate just so they are proud of their own achievements. But the only big common plecos I've seen have been over 10-12 years or age if any one perseveres to take care of them for that long.
And those funny claims about 2feet in no time just condemns common plecos to being abandoned to die in a fish shop, river, lake, or flushed down the toilet in their first few years of life just because people get scared they are going to bust their tank in no time. Common plecos grow steady enough but just about slowly enough for a sensible fish keeper that loves their own fish to expand on time. And they deserve that because they are fish with personality and develop love relationship with their owner.
Mine used to hate me when small, ran away from me making hurricanes along the way. Now he's a sucker for my hand taking him two seconds to swim over to the top checking for treats, and is a big puppy fish often observing me or just coming over when I look in the tank and loving the attention, literally just staring for some reason he only knows...., I find the common pleco way nicer and smarter fish than my small bristlenose pleco for example who is a terminator afraid of his own shadow..
