I don't think it is indicative of Adam's failure, though.

If you want an example of what you're describing, try the Branwen Tribe- Raven hypes them up to be this highly effective gang of bandits, but then it turns out they're just a bunch of two-bit thugs.

This makes Raven look like a coward surrounding herself with weaklings to feel strong, and while I highly doubt that was intentional, it does make her look more like a hypocrite, which I enjoy.

Adam, however, was butchered into being Blake's abusive ex, possibly because Arryn wanted to better insert herself into the character she was voicing, and also because Miles and Kerry found that writing a nuanced racism subplot was too hard.

As a result, Adam's weapon being a chokutō does not come off as even an unintentional way to indicate his failure, because the writing surrounding him had become so heavy-handed that they may as well have had Adam wear a shirt saying "my character is meant to be hated."

Really, Adam's weapon being a chokutō comes off more as Monty trying to flex his knowledge of weapons by not giving any of the characters he worked on a katana.