The argument about power usage for developers, as opposed to consumers, is probably insignificant compared to the inefficient use of compute resources for deployed software today.
Arguably LLMs are probably enabling some web developers to create native applications rather than Electron monstrosities saving many P-core CPU cycles multiplied by the number of their users.
Optimising server applications with an LLM could eliminate unnecessary cloud servers.
Of course all the above could be done without LLMs, but LLMs can empower people to do this kind of work when they were not able before.