I'm delighted to hear that! But that doesn't really counter my argument, which is that if a task can be done by an LLM it wasn't a good fit for a junior anyway. Being able to just fling basic tasks over the wall to GPT is great, and should free up time for non-junior devs -- but since those tasks wouldn't have helped grow the junior devs in the first place it doesn't really affect them or their trajectory. Unless you were just using them to churn through drudgework in the first place, in which case I guess great, you can just purge them from your org at no net loss since they'd have burned out soon enough anyway.
If anything I'd turn the thesis of your title on its head: should engineering leads be worried that AI will take away the last bits of code they should have still been writing?
(Betteridge's law, of course, still applies).