I think I ran across this story in “Military History” magazine years ago. It’s covered in various books about World War I, including Sir Martin Gilbert’s massive volume, or the Bolshevik Revolution, but there doesn’t seem to be a good book available in English about the Czech Legion specifically.
You are correct, this needs its own modern retelling especially how they battled Trotsky’s intention to have them all die.
I read a condensed version of Gilbert’s work when I was working on the restoration of the WWI museum in Kansas City. If this was mentioned in the condensation, I missed it — that was just over 20 years ago.