There are a lot of aftermarket stainless brake lines, that have a 'banjo' fittings instead of a threaded fittings.
I went through this problem 17-18 years ago when I was replacing the OEM rubber brake hoses on my '81 R65, every set that I got had a banjo fitting for the connection to the master cylinder.
I had to personally take my OEM brake hoses to Luftmeister in Bellflower,CA. , and give them to Matt Capri, the owner of Luftmeister, to get a correct hose made up while I waited.
If I remember correctly, MrRiden'82 LS has a master cylinder brake line with a banjo fitting at the master cylinder, installed on his LS.
But there's no excuse for being poorly treated by someone that doesn't know how to listen !!