You are spot on. Even modestly competitive runners had a much better sense of pace before GPS. When I was running in the 1970s, I knew within about 10 seconds/mile how fast I was going at any given time except, perhaps, on steep hills or on a muddy trail. So figuring out how far I went just required use of the simple formula of RATE x TIME = DISTANCE. I had a wrist watch (non digital, of course) to time each run, so I knew for example, that if I ran for 40 minutes at an easy pace of 8:00/mi I had run 5 miles. For tempo runs, I would carefully subtract the seconds that I was stuck at traffic lights. For my log, it was imperfect, but always recorded to the half or full mile, with slight rounding (the "long 10" or "short 10" someone else discussed above). I never figured warm-ups, cool-down jogs or strides into my mileage totals. So true volume was actually more than I recorded.
For long runs, I planned them on a street map before leaving the house. I used tick marks on a piece of paper to mark the length of each straight stretch off the map (and divided curves into straight sections), then used a ruler to determine the total length on the paper. I then compared that to the distance gauge in the map legend to figure out the distance. Then I joined Army ROTC in college and one of the very first things they showed me in my (topographic) map reading class was how to measure distances -- almost exactly how I was doing it on the street maps for running. (Both of my sons are now in college, one studying engineering, and I don't think either one knows how to read a street map, much less use one to measure distance!!)
Now that I am in my late 50s and have been running with a GPS for about 7 years, I have lost much of my ability to KNOW how fast I am going except for -- maybe -- my race paces. Part of that is the reality that my perceived effort is the same, but I am getting slower (aging sucks). But more of it is that I am obsessed with looking down at my watch every 10 minutes to check my distance and pace and let the watch do the thinking for me.
As for the dishonesty, when Gerry Lindgren was running in the 1960s and early 70s, volume was everything. Lots of guys were running over 100 miles/week. Lots of high school kids (including me) were running marathons then and focused most of their training on "LSD" - Long, Slow, Distance. Lindgren's claim may have been dubious. He had a colorful personal life filled with a degree of deceit, so I suspect he was untruthful about 350 mi/week. But it is known that he averaged far more than 100 miles/week.