Correct, more or less. But kman1211 is right that Beyerdynamic was the first "dynamic" headphone - Baldwin's headsets were crystal headsets for radio operators, and not really designed for music listening (they were sold as part of radio sets). You can see a collection of this style of headphones here:
http://oldheadphones.com/crystal/gallery/gallery.html
They use a different driver principle than what Beyerdynamic did with the DT48; they're usually moving iron drivers (Wikipedia has a bit more here: https://en.wikipedia.org/wiki/Crystal_radio#Earphones). They are not "high fidelity" in any sense of the word - they're basically there for communication and functionality over anything else. The impedance is also very high in many cases (multi thousand ohm), due to what they're designed to plug into.
This doesn't mean you cannot listen to music on them (crystal radios can be built to receive AM broadcasts, for example), but they aren't going to provide a similar listening experience to our modern cans in terms of comfort, fidelity, etc.
Beyerdynamic DT48 were "special" because they're a more modern-looking dynamic driver (and rightly the "first"), but they weren't mass-marketed/things were hampered by World War II. If I remember right they tried to bring them to market (/"reintroduce" them) in the late 1940s following the war (they were initially developed in the late 1930s as the war broke out, and per Beyer's own history, released for the first time in 1937, around the same time Koss (in the US) was bringing their first set of headphones out as well, leading to both companies claiming "firsts" with respect to dynamic headphones.
What Klipsch is showing in the video looks like a crystal set, which existed in the '10s and '20s for use with various radio applications. I was kind of annoyed when I saw that Klipsch appears to want to throw their hat into the ring of "look at what we invented!" just for a cheap marketing plug.