Is it a solved problem in relation to hydrogen vehicle refueling?
In theory, yes, we can pressurise things very very fast. It does cost money and space (larger tanks), which makes it impractical for everyday solutions.
I still don't get how hydrogen can be cheaper than electricity, since creating green hydrogen via electrolysis takes around 4-5 times more electricity than it can actually produce. Blue/grey hydrogen is just natural gas, which doesn't make it any more environmentally friendly than just running a straght-up CNG car.
In my country the electricity price could quadruple and it's still cheaper than gasoline or diesel. The closest H2 refueling point is in a neighbouring country. And no one is rushing to put up a comprehensive network of $2 million a pop H2 stations.
An example from Sweden: https://www.h2euro.org/whats-h2appening/sweden-more-than-tri...
News from 2017 about how Sweden will TRIPLE their number of H2 stations from 4 to 12 by 2020!
It's now 2021, almost 2022 and the number of stations is... still four.
(Meanwhile a single supermarket chain in Finland has opened 222 new charging points during Q2-Q4/2021)
This is a huge chicken and egg problem. Someone needs to front up truckloads of cash and bureaucracy fighting time to put up a comprehensive network before regular people will shell up cash for H2 vehicles.