Yanma meets all of the requirements for an LC Pokemon. It's a first evolution but Not Fully Evolved, as it doesn't have an NFE evolution, just Yanmega which is UU.
Archen is in LC and has an evoloution but not one in NFE
Aipom is in LC and has an evolution but not one in NFE
Why not Yanma?
Yanma is not in the LC Tier being as it was banned from that Tier. It used to be Uber LC, but it is way to powerful for it, and was thus banned from the Tier. Same goes to Carvanha, as it is NFE as well.