unnamed characters =/= fodders.
We're told there were other pirate crews who had come there to God Valley, a lot of the people here are in the Vet - YC range, even if they're just "unnamed" to us. For example Newgate had 50 power allied captains who were ranging from Vet tier to YCs...But we don't know all 50.
With Koby we know specifically he was fighting against character pre-TS luffy would've merked. And Silver Axe is a great example of what I mean Oda introduces him with comparison to Shiki, and thus transitive comparisons to Newgate and such as well. On the other hand, in multiple arcs no comparative statements with strong characters exist for Koby.