This happened to me too since 2019.

I think it is a sneaky bug that just got in and no one hardly noticed, but yes, Isometric views export to DWG or other line software aren't up to scale.

I use it often to to Iso views in my 2D cad drawings, and they aren't to scale since the 2019 version, they used to be before.

At first I thought it was some plugin issue (because I use a lot of them and I sometime encounter compatibility problems, but I did a few clean re-install since and it was there nonetheless.

I just kinda live with it now