If you're interested in the subject, that might be a good place to start: https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/...
I guess i'm super conservative about sourcing when reading arguments made about historical topics (and academic papers at least tend to make it clear whether or not their sourcing is primary, secondary, or what).
Especially when it comes to claims of what the common perception was at any particular point in human history i am always curious to see not what someone's narrative is, but what they're building their case upon.
(also as an aside the use of The Last Samurai as a lens or touchstone for discussing bushido was a bit weird to me given how prevalent the notion of bushido is. But maybe i'm just sad that that's the go-to reference.)
Yeah, there's a good chance The Last Samurai might currently be the most popular lens through which people view bushido right now (Americans at least). I share your sadness but I'm sure most people actually have multiple points of reference on the concept. Would be funny if it continued to evolve into something completely different (something featuring Tom Cruise?)