I am more familiar with the CT and AT bikes, but I'll take a stab at it, and maybe someone else will come along and either yes or no my thoughts. We'll both learn, then.
In the CT/AT bikes, there is a release of the kickstarter through the angled spring you see in this pic:
 
The engaging gear rolls outward on the spiral tracks you see on the kickstarter shaft, pushed out by the tab on the spring to the right of the gear. Engaging the lever with your foot pushes the gear back along the spiral track until the gear engages.
But it looks like to me the RT-2 has a different system that keeps the three gears engaged throughout  throughout:
www.partzilla.com/catalog/yamaha/motorcycle/1972/rt2/starter
There just doesn't seem to be any spiral tracks nor sliding gear, nor spring which would push the gear into a disengaged position. So I think your determination that the three gears stay engaged must be correct.
Someone will know more and guide you through my mistakes, if I've made any.

So it's operation is just like the CT/AT's I am familiar with. I was confused as to how the three gears could stay meshed and yet the lever somehow disconnect from the meshed gears! That explains it: Same as the other ones.