Air bearings are expensive and have a very low clearance (talking about tens of microns). The lower clearance raises the issue of safety. If I remember correctly, to get that to be greater than tens of microns you need larger compressors and lower operating pressure inside the tube which increases costs and it tougher to maintain.

If you take a look at the SpaceX Hyperloop competition the teams moved away from using air bearings mostly due to the low clearances and the challenges it brought. Maybe on Mars it could be more realistic.

Is it maglev? Iirc it's a passive magnetic system, like inductrac... Which has recently come off patent.