On Eric Gorr's old site and in his first book, there was mention of a Team Green bulleting on this problem for a KX60 (and maybe others??). It related to three divots in the crankcase in the area you mentioned.
What year KDX is being worked on in the video? Is it a 1989 - 1994 model? I read those models have a problem, but have never heard of a 1995 and newer model having one. Also, how long is the video?
You can use $2 of cheap rope to hold the flywheel steady, then use a $15 Dana Stubblefield Sales puller. I have done it on mine a couple of times.