50p is a steal, counts towards HQ tax (no triple TPE) and he's not locked to a forgeworld. Yep, auto-include.
Not having Canticles and no <Forge World> keyword means he won't profit from other buffs (TPD, Cawl, Manipulus), but the more annoying part is that ALL transports (including the termite) are locked to <Forge World> infantry, so no Skorpius Plasmariders with inbuilt "Screw that target, and don't overheat while doing so".
X-101 seems just...bad. Cheapest elite choice except for Servitors at least, but neither the range to throw around shots while camping an objective, nor the output to actively do anything. I could only see this guy camping an objective by being cheaper than 5 rangers and untargetable, and fill out a brigade detachment.