The developers made a very correct decision for this beast and made a not very large radius of its aggression. If he would have a higher target radius (like a raptor, for example), he will start shooting for the first step, and it will be very annoying for all players.
Never underestimate these bastards, I was trying to tame one of them and THEIR NEEDLES HAVE RANGE! I was on the other side of the lake in the desert biome and I was getting aim boted by thier needles. MAKE SURE TO HAVE SOME MED BREWS IF U TRY TO TAME ONE!