Not the only way.......but they are overthinking the whole thing I believe.
I was mistaken about how much difference there was.......it's more like 5 degrees. I had a couple of odd jugs in the mix. The transfers were lower on those jugs.
When I checked the after machined heights I grabbed the wrong jug.
Al, you are right though.......at TDC and BTD the crank has to turn further to produce piston movement, so piston speed has to be faster at mid point, or 90 degrees than at top or bottom......a sine wave pattern. After all the piston has to stop, and change direction at each end of the stroke. It better slow down some first.
The transfer ports are at 120 opening point on average, and are fully open at BDC. That explains why they move more degrees in crank rotation per .001" of cylinder drop.