I hear the folks who would love to have individual tempo scale on their machines. It’s a useful feature. It’s a quick way to make one or more tracks’ patterns longer (with built-in 3/2 and 3/4 polymeter per-track “presets”) and thus the musical statements have a longer evolution. Maybe the reason only the OT has it is due to those stated above, I don’t know. I have only an OT. And Open Mike is right, if it’s polymeters one is after, the individual step lengths do technically cover that.