At private schools with SAT midpoints 1200 or above AND which do not have extensive co-op or internship programs or religious mission programs, only about 7% of students take longer than 4 years to graduate (average).
The schools mentioned for the 4 year pledge have lower applicants (except maybe cpp) and I am sure a great strategy to woo students. No way at San Diego State, Long Beach State and Fullerton they are making those pledges.
Cal Poly Pomona
The pledge has an “out”, the students performance. If you have to drop a class (like Calc 2 or Thermodynamics), then the student has failed their pledge. All the school has to do is provide “effective” advising and ensure critical courses are available.