You missed one pertinent bit:
Of course, I wasn’t a math major.
If those figures [webpagesthatsuck.com] were accompanied by something even remotely resembling stats (e.g. average based on 100 tests) then I'd be tempted to wonder how and why there might be such a discrepancy
In the meantime, I'll stick with the 80/20 approach to site maintenance; concentrating my efforts on content and presentation