Yeah, stainless tubing doesn't rust.
But if you search, you'll find lots of folks that can't get the stainless flares to seal. Or if they do seal, it's with copper sealing washers, or repeatedly tightening the livin' crap out of them.
Not my first choice.
I built a pair of 3/16 brake tubes from NiCopp tubing. My tooling couldn't make a decent, repeatable double-flare on that stuff. I did eventually get it to seal. I did not have any fun doing it, and I screwed-up a number of flares and then had to cut 'em off.
Plain ol' double-wall seamless steel tubing for me, thank you very much. QUALITY tubing lasts decades. The cheap-crap tubing GM used in the 2000s had a short service life, but that was due to excessive cost-cutting--using crappy tubing on a safety-critical assembly.