shin length to set initial saddle height?

[ucdcrush]

I know that saddle height is something best tuned after various trials, a bike fit etc., but..

I stumbled across the Specialized "Bike Sizing App" (which has Retul branding on it) that includes a saddle height recommendation in addition to frame size recommendation.

https://www.specialized.com/us/en/bike-sizing/app#/

To my surprise, rather than asking about inseam to provide a starting saddle height recommendation, the App only requested shin length. For what it's worth, my shin length was 40cm and it recommended a starting saddle height of 73.4cm. My inseam is 83.5cm and my height is 176.5cm.

I imagine there is a correlation between shin length and inseam among humans.. so maybe it's essentially equivalent to the app requesting inseam.

But made me wonder, since most of the calculators out there are based on inseam.. is there something special about shin length that might make it a better predictor, at least for a place to start for saddle height? I googled saddle height and shin length, and did not find discussion of a direct relationship.