Well, Nikola seems to be a massive scam, so I probably wouldn't believe a single thing that they say. Some short sellers published a report on them and it's scathing to say the least: https://hindenburgresearch.com/nikola/Maybe. If you believe Nikola then HFR is the ideal distance for Hydrogen (400 to 800 miles); the weight of the cells is less than the equivalent battery capacity. I'm not sure battery weight matters as much for a train since the %age increase would be less.
Nikola's response to them is also laughable at best: https://nikolamotor.com/press_relea...n-false-and-misleading-short-seller-report-96