The only time I remember route length coming into play in CHM was, if there are 2+ separate pieces of a same-numbered (or named) route, then the longest one is the "main" piece, without an abbrev.
I don't believe the idea of 2 routes branching apart, with ambiguity over which branch would be part of the "main" piece, came into play; I don't think it had been conceived of back then.
I wanna say this is something that's still not explicitly addressed now -- and probably shouldn't be; most likely best handled on a case-by-case basis.