In multiplayer games, the green speed is set the the highest tier in the game
This is true but in my experience, it's not always a true number. Legends playing with TLs and above will see faster greens but the "above" don"t always see their true speeds.
WGT introduced fractions of speed a while ago. That is to say they're utilizing the decimal points. A mix of Legends and above usually see something more than 12 but less than 13, by example.
This is also what they do during the week to mess with green speeds. What you see on Monday isn't always what you see on Friday. :-)