I actually think the OP has a valid point.
The lack of any Champ speed type greens - along with the fact WGT allows for pretty generous gimme putts to be taken and the green putting tip - makes coin rooms - even easier than regular play. If anything, you could say a lot of players are deprived and denied the opportunity to learn and play C13 greens in coin rooms and in turn becoming slow green specialist. Maybe those players should also be exposed to greater diversity so they can see what they need to work on and be able to progress towards.
Consider this, you find C13 greens in Clashes don't you? Why not coin rooms? They can specify which coin rooms of course, say Rio or Montreal and above.
Enough of the kiddy shag carpet ONLY greens that can be much easier to putt on because you don't have to worry about running a ball 5-10 feet past the hole. I don't even have to worry about those low tier players putting off the green because they will be using the putting tip anyway.
Even if they remain randomized to an extent - at least it offers more of a variety - than the easier slower greens.