How to get 1:1 tunisian stitches for graphgans?

[Geryow]

I recently made a graphgan using Tunisian crochet but the amount of vertical distortion present was not appealing for me. I dont have this issue when doing sc crochet graphgans. I tried to do numerous swatches with a bunch of different tensions (tight, loose, super tight, etc) but they all came out closer to rectangles when the stitch count was a 10x10 square. The photo I attached was a 34x36 graph and while I still think it looks good, I would really prefer to avoid this amount of distortion for other graphs. Does anyone have any tips or links to blogs/videos that could help explain what I'm doing wrong?

[Granny Square]

I don't think you are doing anything wrong, you are comparing 2 very different stitches, why should they both be the same proportion?.  Not trying to be obnoxious, honest, but if SC is a better proportioned stitch for you for colorwork (that is probably designed for sc ), stick with that stitch and leave Tunisian for monochrome or striped projects.

The late great Jean Lienhauser used to be active here, and she would talk about the golden loop to control the height of one's stitches, but I'm not certain that applies to Tunisian (the idea was to control stitch height with the initial yarn over of a stitch, lift it up higher or snug it down lower).  Or this Doris Chan article might be an interesting read about stitch heights https://dorischancrochet.com/2009/01/05/confessions-of-a-lifter/