Not the person you were discussing with, but I have to add that to me the main benefit of using Stubby et al. was exactly the schema that was so nicely searchable.

I currently work in a place where the server-server API clients are generated based on TypeScript API method return types, and it's.. not great. The reality of this situation quickly devolves the types using "extends" from a lot of internal types that are often difficult to reason about.

I know that it's possible for the ProtoBuf types to also push their tendrils quite deep into business code, but my personal experience has been a lot less frustrating with that than the TypeScript return type being generated into an API client.