not really true, fammey, for a number of reasons.
You can see a Level 2 matrix on alphatrade and on other services. Are they real? Are they "unsolicited" bids and asks or just arbitrary MM signals, intended to play a nice game with retail investors? I know they are not just the unsolicited quotes as I typically buy between them.
There are no hard and fast answers out there and I've been hunting, as has Jim, for a long time.