For the mass mass of folks, such as those beginning a search, the only number I see as useful for deciding "does this bike warrant a further look" is the "standover height" and in inches please on this side of the pond.

For my say, I'll say that all SOH's should be measured from the ground up to the top of the top tube at the top tube's highest point. Adding a note to say if the top tube is slanted, etc., is also helpful.

So if I on a burn to buy a used Trek hybrid-like bike and search the local area C/L;
-- I will find about 150 Treks for sale on a typical day
-- It would be great if the add subject line said

"TREK, used 1999 Model 730, XC, Red, 34" SOH, City/State, $price/OBO"

That would aid in quickly sorting out those available that fit the basic criteria

FWIW...
/K