Theory. I have been there. Looks like a lion to me. And lions were symbolic in all of ancient Egypt.
Not a lion’s body. It may look like a lion to you, but anatomically it does not. It fits perfectly with the body of a jackal. Go look at a canine’s body shape and compare that to a lion’s - there are vast differences: most outstanding absent are the lack of a deep, high chest and sloping back of a lion at rest.
Both lion and jackal statues are always portrayed the same way for each. There are no lions carved with a body similar to the Sphinx.
Jackals were held more highly than lions during the First Kingdom for their identification with Anubis Guardian and Shepard of the Dead.
The current form of the Sphinx has been heavily reconstructed since Roman times on the theory it was supposed to be a lion, as you say.
But a lion makes no sense to be watching over that site. Anubis does. Most of the time the Sphinx was covered by sand and only recently visible in its entirety.
“The Great Sphinx Mystery” by Robert Temple has a lot of photos of the Sphinx (old and recent) from many angles. Temple may know more than Zwais about the First Kingdom - without Zwais’ Egyptian-centric islamic political agenda.
There are also First Kingdom references to the Sphinx as being Anubis The Jackal.