109% method...What am I doing wrong?

I've been riding for years and have used the 'heel pedal backwards' method to measure saddle height. I recently realized that I wasn't able to engage my hamstrings effectively so I raised my height about 2-3mm and felt more efficient. Also a slight knee soreness disappeared. I have no hip movement (reaching) and have a slight knee bend at the bottom of the pedal stroke.

I decided to try the 109% method. Wearing cycling socks and cycling shorts I measured my inseam (book in crotch to floor) at 74.5cm (3 times to be sure).
74.5x1.09=81.205cm. Measured from the pedal axle (pedal in-line with seat tube/furthest point from seat) to the top of the seat at center of seat post saddle attachment and found that 81.2 cm was 8 cm below where my seat is currently. I understand that any method is a starting point, but I expected maybe 1 or 2cm, not 8cm.

Did I do something wrong? Since the 109% method goes from the pedal axle to the seat, crank size is essentially irrelevant. The 8cm difference was consistent with my road, touring, ss/fixie and hybrid.

BTW...I'm 5' 10", 210 lbs. and wear pants with a 29" inseam.

I'd appreciate your thoughts. Thank you.