It sounds like you do value creativity and autonomy. If that's the case why would it matter how many hours someone was working? Judge them by their output, not how they got there.
This depends a lot on what the value of their output was. If they want to do their tasks 5 times faster than the interns and leave then they can do that for intern pay since that's the value they bring. If they are actually doing more valuable work that involves understanding the product, working with other teams, designing new systems, and they can still do it in less than 40 hours then that is fine. Being effective at driving projects and making decisions are a different kind of work that usually take some time.