AFAIK, the "wavy washer" is part of the OEM crank setup. Aftermarket cranks that I have seen all are of the "IA" variety which use a "pre-load" adjuster instead (and seems to me 100% better solution).
I can see that if the wavy washer is not installed,or the pre-load adjuster not set, the crank could move laterally even with it tightened to spec. The wavy washer obviously can only provide so much adjustment, and you need spacers if it isn't "semi-squashed" when crank is torqued. I find it pretty difficult to determine how much it is squashed myself, that's why I'm glad I'm now on a Red BB30-IA crank.
scott s.
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