Why are env vars prioritized over explicit settings in models.json?

[mcowger]

Per the docs, the fixed env vars (OPENAI_API_KEY, ANTHROPIC_API_KEY, etc are prioritized OVER the values in models.json:

 {
   "providers": {
     "anthropic": {
       "baseUrl": "https://myhost/",
       "apiKey": "AIHOME_API_KEY"
     },
     "openai": {
       "baseUrl": "https://myhost/v1",
       "api": "openai-responses",
       "apiKey": "AIHOME_API_KEY"
     }
   }
 }

where AIHOME_API_KEY is an env var that contains my desired key. The same behavior occurs with non env vars as well ("apiKey": "sk-SecretKeyHere")

This decision seems really strange to me, as a user-configured value in a non-default file (models.json doesn't exist by default) seems like it should take priority over somewhat generic env vars.

Does anyone have some thoughts as to why this was done this way?