That's exactly what I mean, I'm not sure why they need to put a cap on it themselves. I feel if developers want to make a mistake and use up too much GPU memory, that's their own problem. Putting that limit on there seems like a huge no-no. It's almost like saying "If you want to make a serious game/app that pushes the boundaries of what GPUs can do, don't use AIR."
With Adobe having released Stage3D years ago, I thought their intention was to try and compete with what C++ and other languages can do by directly accessing the GPU. Putting this limit on there seems rather counter-productive. I don't know, maybe they have some good reason for it, but I don't particularly like it. =/ I wonder with enough support, if they could remove the limit.