Yup. Weapon Expertise grants access to weapon-specific feats that have fighter level prerequisites. Including Greater Weapon Focus.This document has been super helpful in designing my newest Samurai PC, but it talks about making use of Deadly Stroke. As far as I can tell, this is not possible without multi-classing into Fighter until level 8 to get Greater Weapon Focus.At the risk of answering without checking references, there's that samurai class feature that lets class levels count as fighter levels to qualify for some feats on a particular chosen weapon (like katana or naginata). If that's not the case, I'm at least close, I think...
Most excellent! Thanks for the replies. My confusion was actually caused my Pathfinder app not correctly applying that rule.