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.
Completely off topic, but I really don't understand the demographic of physics educators that are resistant to Dirac notation in a first QM course. It isn't really that hard to explain or understand, it's extraordinarily convenient, and it's essential for engaging with most quantum adjacent literature. I understand that it conceals the distinction between vector space and dual space a bit but it's really not that hard to get through. I may be biased because I learned the notation in week 2 of intro quantum, so I am curious if anyone with the opposite experience disagrees.
I think he just felt the students wouldn't be able to handle the linear algebra aspects of QM. Strange notion, given that all the students were seniors, and had all taken a linear algebra course from the math department.
Probably wanted less formalism overall.
Like when I took an E&M course in the EE department, and the professor insisted on teaching only the integral forms and not the differential forms of the Maxwell's equations (i.e. no divergence, curl, etc in the whole course).