???
FWIW I have never heard of any “all-important E & M gateway course”. The intermediate E& M course I took Junior year had a number of prerequisite physics courses that obviously needed to be taken as an underclassman . The intro E&M course students took freshman year also had physics prerequisites (intro mechanics), not just math prerequisites. And was not considered any “gateway course”, they were all important.
The engineering school had nothing to do with the physics department requirements, which were pretty typical.
The freshman physics curriculum (non-honors)was out of some very standard physics textbooks which are used ubiquitously across the country, for teaching physics to underclassmen. Sears & Zemansky, Halliday & Resnick, etc.