Maybe he meant the conscious mind we experience abstractly and is somehow hosted in / by the brain.

In which case, sure, it makes sense that each thought blocks the main thread and that's why thought-loops are particularly annoying.

In terms of I/O though, I certainly try to optimize the main thread with concurrent patterns when the input queue gets hit with high traffic. Even if I'm recurrently mulling over something for days, hoping for a break-through or insight or whatever, it's not like I'm incapacitated and can't perform / prioritize other thoughtful tasks on the event loop.