I think there are two ways you can look at this: either this particular alien is behaving in a way we've never seen before, or it's simply doing something we've never seen before.
I tend to think it's probably the latter, as I don't believe the aliens behaviour would be affected by host traits (besides the means of movement and other things dictated by physical characteristics. As to what it's doing and why, I think it's prudent to examine the situation.
We have a single alien acting in a situation where it is outnumbered, just as in the first movie, however what makes this instance radically different is the imminent arrival of a new queen. As we know, this prompts the alien to act in a protective manner toward the host but, if you think about it logically, it doesn't make sense for it to want to kill the other humans indiscriminately. The survival of the species would be far better ensured if the queen could safely achieve maturity with as many viable host specimens left. A single queen and warrior surrounded by a cache of eggs, relying on chance to provide future hosts, is not a good recipe for survival.
For this reason I think what we're seeing is the alien doing something to its victims which would immobilise them for an extended period of time without killing them, either with some sort of venom or toxin or something relating to the hive material. We know that a cocoon seen, similar to that cut from the first movie, was planned for Alien 3, so I'm more inclined toward the latter. If the hive is created through the growth of spore-like organisms secreted by glands in the alien's mouth it would make sense for it to create a great number of superficial wounds on the victim within which it could propagate.
Fairly technical, I know, but it's an idea I find compelling.