*Early entry doesn't always mean reducing the time spent studying.
At my DCs school, they all start GCSE in year 9.*
So having done a year less in KS3. Very few GCSEs are ab initio, with no content assumed to have been done prior to starting the "GCSE" course.
In year 11, if they have achieved their target grades (so not just a C), they can choose more options
The argument that people wouldn't do better in a given subject, given an extra year's study, is pretty silly, though. Those "target" grades presumably allow for the missing year.
they can choose more options, but they have twice as many lessons.
Fortunately, the best 8 accountability measure will put paid to all this sort of gaming.