With one ranked round (RG of 40) between Pro and Master, it all comes from the match wins against higher tiers. Didn't you notice that your average dropped all the time?
You get to TP with a Pro average of 72.0. If you play a ranked round then, this score (x2 for nine holes) will be the starting value in the new tier. But, when you continue with matches only, the (Pro) average drops further from the wins, shortening the distance to 67.00 and Master.
I remember another case where this happened. It's a fairly unknown shortcut.
BTW: You may continue to Tour Master @63.00.
BTW2: I don't know how the one RG score fits into the picture.