The only time I've heard the term supervised solo before is on the first 2 solo flights. But the CFI isn't in the chopper. They will be outside watching,
The first solo, as i'm sure you all know is the hover solo with the CFI watching on and giving hand gestures such as, pick up, set down, hover left, etc.....
The second is the pattern solo with the CFI watching on and possibly in radio contact.
Some places refer to this as "Supervised Solo". Maybe this is what the guy was talking about.