They don't have to get to the same place at the same time, they just all have to cross a finish line. The finish line is the same for everyone, even if the fast track students get to take a more fun route and play doing other things they enjoy along the way.
Certainly the fast track students will still have a competitive advantage since they will probably have worked on more challenging problems, but it fixes the graduation stats. Who knows if it will have positive downstream effects.
Not a perfect analogy, but: due to my AP scores, I placed out of the first two semesters of the four-semester mathematics requirements. After two years, I didn't know more math than those who didn't place out, I just finished learning it a little earlier.
People with existing programming experience will start off at a slightly higher level than those without, but the latter group will end up in roughly the same place, by taking an elective or three fewer.
And even if they don't, so what? Maybe someone with more experience ends up diving deep into OS design, compiler writing, and database design, while someone with less experience only gets to dive deep into database design. The CS program has still prepared both groups for their first job after they graduate (or their masters/PhD program, if they choose that route), some people might just have less or more to learn later as they grow into the rest of their lives. This is true of pretty much any profession; programming is by no means unique here.