You didnt have 10 of them running though.
You want to do that, but Ill bet money you arent doing it.
Thats the problem: this is speculative; maybe it scales sometimes, but mostly people do not work on ten things at once.
“Fix the landing page”
“I’ll make you ten new ones!”
“No. Calm down. Fix this one, and do it now, not when youre finished playing with your prompts”
There are legitimate times when complex pieces of work decompose into parallel tasks, but its the exception not the norm.
Most complex work has linked dependencies that need to be done in order.
Remember the mythical man month? Anyone? Anyone???!!??
You can't just add “more parallel” to get things done faster.