I use that technique to come up with the maximum standover height that I can tolerate. Then I look at top-tube length. For example: Jamis had some models that interested me last year, but when I went to large enough frame size to get the top tube length I wanted, the standover height was greater than my inseam measured using the above method. So I looked elsewhere.

In other words, I use the standover as a secondary item, not as my primary guide in sizing.