You seem to have read the chart completely wrong. You took Scale 4 as the example of getting a 3.9 with an 84%. Look at the legend underneath. Only applicants from the Royal Military College of Canada have their grades converted under Scale 4. Very, very few applicants come from there. Even if ALL of Canadian student applications came, by some freak circumstance, from the RMC, it wouldn't apply to American applicants. This chart is only for Canadian university graduates. When I quoted 3.9 as being a 90% average, that's just echoing average matriculant grades I'm aware of for U of T (seeing as most U of T applicants are from Ontario and are under Scales 3 and 7).
It depends entirely upon an applicant's transcript and what sorts of conversion factors are listed there, and if percentages or letter grades are used. I don't know of any American applicants to Canadian schools in the first place, so I'm not sure how it would work, but it certainly wouldn't be 84% = 3.9.
Thank you for compiling data on Canadian schools, but unfortunately your argument doesn't really hold true, and you appear to have misinterpreted the data. If Canadian applicants bemoan the difficulty of getting into Canadian schools, it's because it truly is difficult (from an academics perspective).