The style is certainly similar.

Here's Murray's text on it - I think she may have thought the Osireon was Old Kingdom althogh I've not read this.

As the stone for Khafre's was brought from Aswan, there was certainly granite stone work being transported past Abydos during the Old Kingdom, and we know Abydos was the early dynastic royal necropolis, so there's no reason per-se that it couldn't be old kingdom.

As for the detailed evidence, well here's the text:

[www.case.edu]

Dave Light.