It lacks the ability to self correct and do all the adjacent tasks like client comms etc. So if I come back to it in the afternoon I may have wasted a day in business terms, because I will need to try again tomorrow. What do I tell the client, sorry the LLM failed the simple task so we will have to try again tomorrow? Worse, lie and say sorry this 2 hour task could not be achieved by our developers today. Either way we look incompetent (because realistically, we were not competent, relying on a tool that fails frequently)
I'm sorry but I'm not familiar with the context you mention, have not worked in a job where I had to communicate with clients and I find it hard to imagine a job where a junior would have to communicate with a client on a 2 hour task. Why would you want a junior to be the public face of your company?
Digital agencies often trust their developers to interface with their clients. These are tight, trusting relationships built between two technical or tech adjacent teams in most cases. To say they are a public face would misunderstand the relationship a bit, both teams have juniors and our juniors have high expectations of professionalism and execution.