Hi saltab, so the upshot is that there is an "Isometric scale" (your 1.225 value) that you need to apply if you want to make isometric axis lengths preserved instead of view plane lengths preserved.

Some info here:
https://www.jntukmaterials.com/wp-content/uploads/2019/05/textbook-of-engineering-drawing_compressed-4-2.pdf
https://rskr.irimee.in/sites/default/files/Isometric%20Drawings.pdf
https://gppanchkula.ac.in/wp-content/uploads/2020/04/Axonometric-projection-.pdf

- Michael

Hi Michael!

I thought that number should have an explanation... I am glad to finally know where it comes from! :)

Many thanks!
Salvatore