The Top Gear video mentions that kind of recharge time using an external system (though they do claim that they are trying to get it down to 30min).

I've seen some claims that the gas is stored at a pressure of 10000 psi/690 bar in a 200 l tank. If that's true, then that is a gas volume of 138000 l. A commercial, stationary scuba compressor compresses around 850 l/min [0] to 350 bar. A compressor like that would take around 160 min just to compress 138000 l to 350 bar (so significantly less than 690 bar), is a _large_ appliance, and _loud_. Compressing gas quickly also produces heat. An on-board compressor seems quite unrealistic to me unless I'm missing something.

[0] https://www.bauer-kompressoren.de/en_en/pe-ve1