The Government doesn't approve GCSE sysllabuses; that's the job of Ofqual. (The DfE has input into the overall system but not to individual syllabuses).
Further, there's no such thing as the GCSE History syllabus. Each examining body (AQA, CCEA, EdExcel, OCR, WJEC & CIE) is free to determine its own syllabus, subject to approval by OfQual. Most (possibly all) of those examining bodies offer alternative syllabuses within the subject, so there are lots of different GCSE History syllabuses.