I think you hit the nail on the head with the analogy to Doctor GPT, but I think you missed it with gatekeeping. I don't think it's about gatekeeping at all.
A freelance developer (or a doctor) is familiar with working within a particular framework and process flow. For any new feature, you start by generating user stories, work out a high level architecure, think about about how to integrate that into your existing codebase, and then write the code. It's mostly a unidirectional flow.
When the client starts giving you code, it turns into a bidirectional flow. You can't just copy/paste the code and call it done. You have to go in the reverse direction: read the code to parse out what the high level architecture is, which user stories it implements and which it does not. After that you have to go back in the forward direction to actually adapt and integrate the code. The client thinks they've made the developer's job easier, but they've actually doubled the cognitive load. This is stressful and frustrating for the developer.
A freelance developer (or a doctor) is familiar with working within a particular framework and process flow. For any new feature, you start by generating user stories, work out a high level architecure, think about about how to integrate that into your existing codebase, and then write the code. It's mostly a unidirectional flow.
When the client starts giving you code, it turns into a bidirectional flow. You can't just copy/paste the code and call it done. You have to go in the reverse direction: read the code to parse out what the high level architecture is, which user stories it implements and which it does not. After that you have to go back in the forward direction to actually adapt and integrate the code. The client thinks they've made the developer's job easier, but they've actually doubled the cognitive load. This is stressful and frustrating for the developer.