Schoch is considered a kook in the scientific community because he has a conclusion to which he fits the data. Moreover, he ignores other data and possibilities because they don't support his conclusions.
The sphinx almost certainly did not exist before the pyramids of Giza and was carved in the likeness of Khafre around 2500 BCE, the pharaoh for whom one of the pyramids was built. The sphinx "stands guard" at the end of his causeway.
We can dismiss the 10,000+ claim since there's no evidence of the sphinx motif in Pre-Dynastic art and murals. Moreover, there is no evidence of settlement in Giza in Pre-Dynastic times (they were more prevalent in the Delta). The greatly exaggerated age of the sphinx fails to take into consideration the data presented by Colin Reader and at least one other geologist who studied the sphinx, both agreeing that, while it may be a few hundred years older than previously thought, the inundation from the Nile, acid rain, condensation and capillary response of the rock, etc. are likely to be at work.
Also ignored by the exaggerated antiquity claim is the even more parsimonious explanation that the builders of the sphinx simply modified an existing limestone hill (this was where they quarried some of the rock for construction in the pyramids & temples) and built around it, covering previously weathered rock. The original facade of the sphinx is long gone.