One of Xonxt's diary entries mentions the reason, why can he wield two Hivehands - he doesn't produce "honeydew" like the Grunts do, so the highly territorial hornets won't fight over it. If that is the case, why couldn't Gordon, Adrian or other humans have Hivehand akimbo, especially considering that Vortigaunts are physically weaker than humans (as stated the reason why Xonxt can't use human guns - they kick too hard). More importantly why don't one Grunt's hornets attack another Grunt's hornets?
In the final cutscene of the game we're treated to a glimpse of Freeman himself swiming away from the dam. Shortly after Xonxt is also blown into the canal and later is washed out just as JustBarney and Kate are driving by in their pickup. Now remember that in Azure Sheep JB also briefly got to Xen, which happened shortly after Freeman got to Xen. And when he returned it still took a lot of time and combat until he and Kate finally reached that pickup and escaped. Considering all that how long has Xonxt been flowing through that canal?
Actually if you remember the canal in original game it didn't enter any pipe or duct. The pipe enterances, through which Freeman proceeded further, were above the water. There was actually no way the canal could convey passed-out Xonxt to the meeting point.
