Many software engineering adjacent courses, starting with AP Computer Science A, are heavy on the Java-style OOP. And you're never designing an actually complex system, just using all the tools to "properly" abstract things in a program that does very little. It's the right idea if applied right, but they don't get a sense of the scale.

The first place this bites a new SWE in the rear, the database. "Let's abstract this away in case we ever want to switch databases."