Leathercraft Techniques

Hi all! I would like to discuss the Hermès technique for gussets, here is a video showing their perfectly rectangular ones, not trimmed at the angles to give it a round aspect like many do:

And here is what i call the most mathematically accurate technique, trimmed angle in reverse (@3mn24s + @12mn15s) :

Aesthetically wise, i really love the Hermès result, slick and stitches close to the borders, but i don't understand how can you not trim the angles and obtain these sooth edges. Accuracy wise, i prefer the "angle reverse" technique above as everything falls into place precisely, but can i obtain the Hermès result with this above technique? I do not consider the rounded angles as it does not fit my way of doing things.. Thank you all!