Phew I thought this was just me.
It's like you said , Infinite's long cooking time , the Slipspace engine, it means the game is a complete anomaly development wise . GDC is a good shout but they still haven't lifted the lid off this thing gameplay wise , and I think after 5 years they want to do that at the biggest stage possible.
Infinite goes big at E3 , revealing campaign and multiplayer , ending with a beta announcement near-shadow drop, like within a week. Maybe the game wasn't ready for a December beta , or maybe 343 are more confident in this product and even post-E3 feel they can react to feedback quicker with Slipstream.
