Not true. We do not know if the host species cause larger change then a slight difference in physical appearance.But since "that we know of" covers an infinite amount of information its also pointless.
I'd even go so far as to say that since we've seen other types of hybrid do things we've never seen the human/xeno-hybrid do, it makes more sense to assume the host animal has a much greater impact on physiology than mere appearance.
Injecting multiple live fetuses straight into the host body, rather than the egglaying/two stage cycle could very well be a trait of the predator speieces.
If it was a trait of the xeno-species, we should have seen it used a lot more as it would be much more efficent than the whole egg laying stage for a continous colonization, while egg laying would only make sense when approaching a dormant state.