I used this technique all the time… but it’s not limited to seam length. It could be for example checking if the Chest, Waist, and Hips match up to a person’s measurements within reason.
Here’s a pattern from an Annie vest we did. The 2 lines are the aggregate of all the formula lengths that make up the chest and waist.
Hovering over the end points would give me 1/2 the lengths, which I would double and check against the actors mesurements.