HTupolev

Prior to the mid-1980s, outside of some "racing" models, it was very normal for road bikes to take tire widths comparable to what most "endurance" road bikes handle today. 28mm-32mm was pretty normal for stock tire sizes, and even 32mm sometimes left very generous clearances. Here's my '79 Fuji, handling 27mm tires under wide full-length fenders just fine:



This particular bike also came stock with a 110BCD crankset and a rear derailleur with around 35 teeth of wrap that can handle cogs of at least 32T. Originally the bike had a 36-30 low gear, on my current setup it's a very similar 34-28, both of which pretty normal by modern road standards. Granted, this bike is an exception: most old road bikes do have very narrow gearing range (frustratingly, for no apparent real technical reason).

I do agree that, on the whole, most current road bikes are more reasonable for graveling than what Jobst Brandt rode. That the article that's being referenced explicitly says that Brandt was repeatedly snapping his frameset makes it fairly questionable to use as proof that those bikes were well-suited to the task at hand.