I am sure you're right, back then it would have been more like seven. In the 40s I think is when 6-man (6-2) lines came in and eventually
the 5-3 to the 5-2 to the 4-3 with the 6-1 umbrella kind of in between the 5-2 and 4-3. Though 5-2 and 3-4 kind of similar the 3 man lines were popular in mid-70s and 80s ... now, you see these 2-4-5 schemes where the 2 of the LBers are standing ... or they could be considered DEs as well . . .
but it's really 2 DTs and 2 edges ... funny how it's gone from so many to so few ... as passing has taken over. these are college football in the early 1900s, pre-NFL ... kind of a mess