I’ve read that centre lock are better for road because of the extra forces generated due to the grip of the tyres on tarmac.
I think it’s simply a misunderstanding of how loads are applied to a disc brake.
the loads applied to the disc’s connection to the hub have very little to do with tyre grip, and more to do with kinetic energy (good old 1/2mv^2) generally an MTB will be a bit heavier but possibly not moving as fast, where a road bike might be decelerating from a higher speed, but will often weigh less (ignoring the meat sacks sat on top of these hypothetical bikes of course).
Broadly speaking I would expect the rotor on either type of bike to see about the same amounts of torque at the hub connection, both means of connection are more than adequate so I wouldn’t let it sway the choice, Base it on wheel weight and/or price instead maybe…