It is obvious that the Surface Pro DOES NOT NEED AN ADAPTER to Miracast.
My Surface Pro I puts the start screen on the TV for a second or two and then SOMETHING cuts it off.
The TV is still in mirror mode and waiting for a signal.
It appears the Surface tablet realizes it is Miracasting and changes the Miracast frequency or some characteristic so that it only works if you have a Miracast adapter to change the signal back so the TV recognizes it.
Since my Start Screen DOES appear on the TV when I start Mirror mode on the Sony UHD TV for a second or two it PROVES ( at least to me ) that no adapter is actually needed or the Start Screen would not be able to show up on the TV at all without the adapter, but it does.
I believe they are stopping it on purpose to force people to buy adapters.