Autism progression

They certainly can do - and it's not uncommon. With autism being a developmental condition, core symptoms / traits / difficulties (ie diagnostic features) become evident during our early childhood. But differences can also become more evident as children grow older, including due to social demands exceeding our abilities to cope with them.

Some "signs" will change, some will stay the same, some will be old, some will be new.

I'm not sure that "progress" can be applied to "signs" of autism.  We respond to our surroundings and our bodies, 'in the moment.' Things are ALWAYS changing, both with our own bodies and with our surroundings.

That's my best guess, although I appreciate it is word soup and arguably pedantic.....but rest assured, it is not proffered with those intents.