Quite a lot of high end frames (especially those custom-built) are made with a mix of tubes, including from different manufacturers.
For example, in the on-topic era, it wasn't unusual to build the main triangle out of normal gauge Reynolds 531 with forks and stays in Columbus SL, for a light frame.
I have a KOF frame built with 5 different types of tubing: SL, SLX, SPX, 531, 725. What tubing decal did the builder put on? None!