If people that already have some related knowledge have an easier time studying, that's just life. How does it unfairly disadvantage you, if somebody else is already more skilled than you?
Consider two students, one whose education path in the course is exponential and the other whose path is logarithmic where both paths intersect at the end of the course. According to traditional grading the logarithmic student would score far better in the course despite their knowledge being equal to the other student by the end.
Which student would you rather be? who has more potential?
Should the body of a course be treated like a series of 100m sprints or a marathon, and what is the net positive outcome through each approach?
They get graded from the very beginning, not from a single final exam
Student A comes in barely meeting the prerequisites and struggles with low grades on initial tests and projects. They come to office hours, put in substantial effort, and eventually ace the final projects and tests.
Student B comes in with substantial background experience and gets decent but not stellar grades on all tests and projects.
Depending on how much weight is given to the final tests/projects student B may still end up with a higher grade despite the fact that they probably do not have as strong an understanding of the material as student A.
I've had both kinds of students the handful of times I taught graduate-level seminars and it's one reason I weighted the final projects more heavily than initial projects. (Though I found grades on initial projects were still useful for other reasons.)
If Student A ends up only at 80% then so be it, but if they end up matched then they should end up with a similar grade.
In the same way that not being a genius is a disadvantage. Cant change it unless we handicap the smart people.