Purely hypothetical but I am left to wonder if this garden complex was a nursery for plants obtained through foreign sources, namely the Levant. We are reminded of the Palermo stones account of Sneferu bringing back 40 ships full off presumably cedar wood from the Levant.
If these were semi mature plants and trees, then they must have originated somewhere.
It may have been a pleasure garden for the nobility - a forerunner of the Gardens of Babylon. With walls 5m thick, it certainly wasn't just some commoner's backyard.
Sort of makes one wish that one could be a temporary time traveler and stroll along the Nile, wander around the garden and temples, and chat to the intelligentsia and try to find out just what was going on.
BTW Any idea what the large rectangular impression to the left of Unas might be?