I mentioned above that the offense was limited, but to be fair, most offenses were pretty limited until the rule changes in the 80s that opened up the passing game. Penn State was not unique in the emphasis on the run game (including the I formation, the wishbone, the veer) and in lack of scoring proficiency. Most teams in the major conferences and major independents were pretty much the same that way. There were some exceptions, of course, but look at scores in the Big Ten, the SEC, the old SWC, even the Pac8/10, etc. from most any season prior to about 1983 or '84 when the rules were loosened and coaches figured out how to take advantage of that. Once many of those teams got to 20 points, they were almost assured of winning the game. Innovation came to the run game before the passing game. When the veer and the wishbone came about in the later 60s, most other teams did not know how to to stop it, or simply did not have the players to match up effectively even if they had a good idea of how to stop it, or control it.
PSU's big win over Texas in the 1971 season Cotton Bowl, where we held them to no TDs for the first time in some crazy number of games, was the blueprint for how to control the 'bone... if you had the personnel to do so.
This is why we long-time PSU fans would have loved to see the 1969 PSU-Texas matchup. The 1971 PSU Defense was great, the 1969 defense was better. Give Joe a month, and he could dissect just about any offense or defense, or create something that would give a different look to the other team, who would not have time to counter.
OL were restricted on how they could block, not allowed to use their hands, so the technique was all forearms and shoulders. Offensive holding was a 15 yard penalty, not just 10, and seemingly was called more frequently because of the limited ways an OL could legally block. A 15 yard penalty on O was a drive killer. A great OL and great running game, as PSU almost always had under Joe at that time, was the key to winning. Joe and most coaches believed that you won first on defense, then on special teams, and then on offense. Avoiding mistakes and turnovers was paramount, even more than today. Making the other guy go 80 yards without making a mistake or a turnover was the primary philosophy on D, and doing that vs. the types of defenses and the great players PSU and others put on the field was a tall order.
Once the rules changed to open the O, PSU and others had to adapt. PSU in 1982, even before some of the rules changes took effect, was the first team ever to have more offensive yards passing than running. Joe et. al. knew how to adapt to changing rules, but he and the vast majority of other coaches still believed that the key to winning was through a solid D and a sound running game. That may still be the case today, even in this offense-first era, just knowing that you probably need 35 or 40 points to win most games rather than 17 or 20!