For Mame140 and up, I just found out that all games with a frequency of 61.035156Hz doesn't get throttled properly when triplebuffer is active. The result percentage is not 100.00%. If refreshspeed is active it should be 99.00%, but it's not either.
With Mame139 and lower both refreshspeed and triplebuffer are active and the result percentage is ok.
I'm not sure it relates to refreshspeed alone anymore.