Yes, as I said, I'm not entirely sure.
It could also be that the newborn's attack on the queen wasn't just this one Bud Spencer blow, but that it lasted longer.
I think it was in the novel, I'll check it out.
update:
OK, I checked it.
The newborn didn't have a fight with the Queen in the A4 novel, but it attacked her for a longer period of time and didn't just give her a punch like in the film.
The newborn also ate parts of the dead queen and then grew a little bigger.
Unlike in the film, there were several warrior aliens in the nest here, but with the death of the queen they became disoriented and didn't know what to do.