I think if we are honest the early pre-streched lines like double strengh were rubbish and no body in there right mind used them.
Someone must like it a lot though as 35 years on and it's still selling.
I think lines pre the mid 1980's may have seemed simpler to understand because there were nowhere near so many brands and options available as there is now. My local shop - which I worked in late 70's early 80's - had, apart from trout leader mono (so like Kroic) , Maxima, Aiken Bayer Perlon, Platil & Shakespeare Omni. There may have been another (Sylcast likely) but I cannot remember it. The BIGGEST sellers by far were Maxima & Bayer Perlon and Bayer Perlon easily outsold Maxima - probably because it was much cheaper. Everyone, and I mean everyone, asked for line by BS. Diameter was virtually irrelevant. I was one of them.
But that was then. Now I only think of diameter. The BS is whatever it is as I have a very good idea of what it should be or is likely to be.