Not specific to Alpine: Cummins has a 2022 article addressing their view[0] of internal combustion hydrogen vs fuel cell. Short version: fuel cell + battery works well for peaky loads. Hydrogen internal combustion works better for heavy, consistent loads.

[0] https://www.cummins.com/news/2022/01/27/hydrogen-internal-co...

expensive catalysts required for fuel cells?

Because hydrogen fuel doesn’t make sense in any form. It is the darling of petroleum executives. Any engineer or sane person who pokes at it will see it makes no sense.