Education serves two purposes: Understanding and developing skills for employment. Unfortunately, there usually isn't enough time to teach both for all subjects. The latter usually takes priority.

I saw this happen twice in my university life. I took the honors version of CHEM101. 80% of it was more about exploring and discovery, and 20% was more traditional problems, calculations, etc.

For people like me who were not chemistry majors, this was great. For the chemistry majors - they really struggled when they got into CHEM102.

The same happened with Quantum Mechanics I. The professor didn't want to teach all the bra-ket notation, and more or less skipped much of the linear algebra aspects of QM - focusing on a purely calculus approach. He then retired. The professor who taught QM II saw what the professor did, and said "WTF?!" He spent most of the semester reteaching QM I.

As a result, those like me who went on to grad school had to retake QM II at the new university to make up for all that wasn't taught to me.