I also have the same problem. I posted it 2 weeks ago here ( Meshformlines underperform in Rhino 8.0 - Rhino / Rhino for Windows - McNeel Forum) but I didn’t get a reply.
@theoutside I have an evaluation version for Rhino 8, and the latest version seems to be v.8.2. Is it because I use an evaluation version that I cannot get the 8.4? I need to check the MEshFromLines command in a bunch of files.
Edit: Even in 8.3, it’s not working for me.
As for @Ansen.A 's case, I get this result in 8.3:
