Mecanim Root Motion 'loop match' bug

There seems to be a slight bug in the 'loop match' feature whereby even if it indicates green, your looping motion may not be seamless.

In the attached if I define End to be 986 then loop match will be green. However my repeating loop, in this case for rotation, is not entirely seamless. There is a slight jump between loops. By a bit of testing I discovered I had to change the end frame to 985 to get a seamless loop even though according to the red light, my loop should not match.

Anyone else notice this?