Interesting. I'd been shown long ago that split lock washers are useless and quit putting them on anything altogether (my favorite is when they're used in conjunction with a flat washer, which takes them from "almost useless" to "completely useless" and I instantly question the engineering of anything that shows that in the instructions. Many, many aftermarket accessories use that type of crap and you'll notice that you don't find split lock washers anywhere on a modern car except maybe the starter studs. I do wish they'd tried metal pinch locking nuts and serrated flange lock nuts, probably didn't show them because they work better and go against their sales pitch.
Majority of problems with bolts working loose are in applications of heat cycling (header bolts) or sheer forces when the holes are drilled larger than necessary and the parts can shift in sheer (converter bolts). But I've literally installed around 1300-1500 transmissions back when I was an r&r man and never had problems with converter bolts coming loose.
If anyone gets the chance to read the book "engineer to win" it covers this type of stuff, this post makes me want to purchase it and read it again. Also makes me want to see unbiased data from these locks vs pinch lock and serrated flange locking nuts
