I wanted to make a joke about that, but in seriousness, I would guess that the term "Long March" in contemporary Chinese culture, through the legendary status of that heroic campaign, has become rhetorically synonymous with a personal journey of perseverance and struggle basically akin to how Western cultures use the term "odyssey" from "The Odyssey." It's (justifiably) become one of those culturally enmeshed figurative terms, like how TERF island likes to append Dunkirk to the end of everything: "financial Dunkirk, political Dunkirk, etc."

The title likely is an allusion to that or maybe laconically pointing out just that the protagonist absolutely gets their daily steps in because they've meandered all around Tang China.