This method doesn't account for crankarm-length and leg-length. Someone with short legs and long crankarms with a 25-degree bend at 6-o'clock would be over-extended at the bottom of the stroke. Conversely, someone with long legs and shorter crankarms with a 35-degree bend at 6-o'clock wouldn't get enough extension to fully utilize their glutes.

I prefer methods that makes measurements when the crankarms are at the bottom of the stroke (parallel to seat-tube). This accounts for crankarm and leg lengths.

Seat-height also is related to the type of riding you do as well. On my mountain-bike, the saddle is about 6-7mm lower than my road-bike. The touring-bike's seat is 4mm lower than my road-bike. On my track-bike, it's 5mm higher than my road-bike.