Historically, there were other fish to fry. Put those other fish on hold and the required number could appear. Also, making proper use of Benghazi allows shorter trips, which effectively increases the capacity of the trucks already there by making the round trip journey (port to front and back) some 2000 km shorter.
So, you are gambling on Stalin doing nothing in your backyard while you are occupied in closing the Western entrance to the Med and moving sufficient motor transport to North Africa?
Quoting your link again
Particularly crippling for the Afrika Korps was the severe shortage of trucks needed to move supplies over the vast distances of the area of operations. In his work, Panzer Battles, German Major General F. W. von Mellenthin pointed to this problem—
Even when our supplies did reach Africa, it was no easy matter to move them to the front, because of the great distances involved. It was 700 miles from Tripoli to Benghazi, 300 from Benghazi to Tobruk, yet another 350 from Tobruk to Alamein.
That is 650 miles when 200 miles was considered to be the maximum for effective motor transport.