There's no reason the MNT Reform cannot be used both on the go and in a docking station.
The parent likes to use an "old fashioned" (I disagree with that judgement, but fine) paradigm of portability, so what? Does that make it a less valid choice? "Portable" is a generic term that's not reserved for discussions of any specific kind of portability, so why not coin/use a specific term for "fits in your pocket and is usable on the train" if you need one, rather than silently assume?
The parent likes to use an "old fashioned" (I disagree with that judgement, but fine) paradigm of portability, so what? Does that make it a less valid choice? "Portable" is a generic term that's not reserved for discussions of any specific kind of portability, so why not coin/use a specific term for "fits in your pocket and is usable on the train" if you need one, rather than silently assume?