Never underestimate the power of bad form You can't assume good form in either foot position. The rider could have other things wrong with their form that could negate any chance at a useful finding in any test.

To my way of thinking a rider who normally pedals with his arches over the pedals would be producing suspect data in a test. I do not know if that is the case with the OP or not, but it seems likely.

While I really don't think the testing is worth doing, it would be interesting if the OP followed through with it and reported back with his findings.

There are facets of bicycling (BMX, trials, etc.) where foot retention is generally not used and I don't see those guys pedaling in this fashion. The only folks I see doing that are people I don't consider to be bicyclists based on other aspects of their riding form and performance. I've got to assume there is a reason for that.