Good points, but the 70s headphones that I know are all midcentric, not just the monitors.
I owned K370 and heard some orthos. I also have Fostex T40RP right now on my head and it's the only vocal monitor. Unfortunately I know also some less expensive headphones including the common man's Sennheiser HD414 and boy were they awful. K370 only covered the full-ish range because it was a dual driver. After that model bass in AKG really went extinct. Stax had the same issue. They were all midcentric headphones even though they were not studio workhorses. The tuning back then was just mostly mids. They were close, some were better than an average headphone today, but the general trend is quite clear. Yamaha was probably an exception, although today the age might obscure that, because they lack extension. The Soviet Echo headphones that are easier to find where I live are plain midcentric like the rest of them.