Wow, way to misread people.
"We've never seen the stage between a burster and an egg-laying Queen!"
"Yeah we did. In AR"
"But it was in a cage!"
...uh, what? Yeah, it was in a cage - How does that suddenly not make it the transitional stage between burster and adult?
The 'Well, they're adaptable' excuse is also crap, because there's no limit to it. If we use that to defend any change, we could easily have flying Aliens that barf adults and fire sub machine guns made out of whale bones because, shit, they're adaptable.