Shrek will step up normally as well, he only does this, when I'm too far away, like when he's on the playgym, and I'm on the computer... He just tells me he wants to come up... and who can resists, lol... He can reach further going backwards...
I think all the Corellas (Bare Eyed Cockatoo's) play like that... No doubt they'll need to be comfortable within the family... If I have visitors Cory doesn't know, he won't do it. In fact, he takes quite a while to warm up to someone new... I had visitors from Denmark (family) for 5 weeks last year, and in the end Cory would take treats from them, and would play on my lap, but never on the floor.