I know that in some ways I am way more immature than my peers and in others I am quite the opposite.
All my emotions are extremely easy to read and I often feel things quite strongly and express this physically or I feel I will explode. For example, if I'm happy I tend to bounce, clap or flap my hands, and may start skipping from foot to foot. Can't really control that but it's been labelled as 'cute' or childlike by my peers when I apologise for it because I know it is weird. I also can be quite naive or just in general act in ways that are perceived as younger than I am.
On the other hand people see me as very mature because I apparently have more sense than most people at my age and have the correct priorities. I've gotten this all throughout my life. While I can't speak for all of us, maybe for some of us we just are sometimes immature in some ways and perhaps more in others? That has at least been the case with the few fellows on the spectrum that I know.