Groh's in particular was read and react....not very aggressive at the snap imo
The following is my lifetime recollection of defensive changes in college football, relative to read and react:
Read and react defenses matched up well with the offenses in the sixties to the eighties (before the spread-the-field formations, rule changes helping the offenses, and the explosive runners and great throwers). They are opposite of the assignment, more aggressive scheme defenses, and require good instinctive pursuit players who can defeat blocks, find the ball, move laterally quickly, and tackle (PJ Davis type player). The gap attacking defenses restarted around 35 years ago about the time the offenses begin to spread the field pre-snap.
Bud Wilkinson (copied by Dodd) was credited with the Oklohoma 5-4 read and react defense used by many teams from the early 50s to the 80s. It became outdated when the spread-the-field offenses dictated more coverage and led to the 4 man line. Strangely the 4 man line is a morph of the old 6 man (gap attacking) defenses used prior to the 5-4. My HS coach moved from the 6 man line to the 5-4 because it was more effective AGAINST THE OPTION just becoming part of offenses in the early 60s.