All the X's I've seen that had Monte Carlo stocks did not have the adjustable comb. Which is a blessing in disguise. When I bought my XT Combo I bought the Monte Carlo stock and had the adjustable comb and butt plate put on. The after market price on the adjustable comb is right at the price of Browning's factory hardware.
I have one XT that had the OEM hardware, and with the comb adjusted extreme right and up 1/8" I couldn't make the adjuster tight enough to hold the comb in place; it kept dropping. I made some spacers out of nylon bushings but eventually had the OEM hardware removed and replaced with more reliable gear.