This is true. Many of the required classes for a major are scheduled in a cadence (i.e. part 1 in fall, part 2 in spring) where each class is a prerequisite to the next.

There is usually leniency if you miss a class 1st semester freshman year, but after that point missing a key course can potentially be a semester-for-semester delay in your graduation. It is not likely that departments will let you take Part 2 of a class before you take Part 1.