In the early Aliens movie it’s mentioned that the Xenomorph’s blood oxides into acid. So maybe the combination of being under tension and the tongue’s material created an air tight seal?
The Xenomorph could have lunged forward to attack her with its tail, surely? Maybe it’s super sensitive in that spot so couldn’t be it’s usual cunning self?
My explanation for the Xenomorph’s erratic combat effectiveness?
I am wondering if their cyber brains have additional skills programmed in that they aren’t aware of, such as fighting, driving, etc.
When BK is talking with the girl she mentions their brains being super computers so they are very quick to assimilate new information. They also have adult motor control skills so they have possibly had some ‘skill’ programmed in.
Also possible that we didn’t see any of the ‘learning to walk’ stuff because of time and/or it being waved away because they are in adult bodies.