I don't doubt the claim it's a variant. If it was an original design, the Isreali manufacturer would have marketed the hell out of that fact. With the exception of the penetrator, everything else is almost the same designwise. I don't think the M111 has a monoblock penetrator. It looks like it telescopes (rod tube penetrator concept) which would help explain its performance vs T-72 frontal turret armor.
Also, the SBwiki entry is incomplete and misleading because they did more than just add 16mm more armor to the T-72 glacis. It doesn't mention the 180mm additional laminate armor under the 16mm plate.
From Armor, Sept-Oct 2006:
The Soviets decided that the best solution was to redesign the glacis of the T-72A MBT specifically to defeat Hetz ammunition. Up until the testing at Kubinka, the T-72 series tanks were protected by a three-layer laminate glacis with an outer layer of high-carbon steel, 80mm thick, a middle layer of "steklotekstolit" or glass-reinforced plastic (GRP), 100mm thick, and an inner layer of high-carbon steel, 20mm thick, for a total thickness of 200mm. The Soviets decided to maintain this alternating steel-GRP-steel laminate design, but increased the number of layers from three to five. The new five layer glacis design had two outer layers of high-carbon steel, two middle layers of GRP, and one inner layer of high-carbon steel. Additionally, the Soviets added a very hard 16mm thick steel faceplate to the outer layer of the glacis. The faceplate is easily identifiable by the two "cookie-cutout" holes cut into the plate to allow it to be placed over the tank's two tow hooks, and welded directly to the outer layer ofthe glacis. For vehicle identification purposes, the faceplate became the defining feature of tanks fitted with this redesigned glacis armor. In effect, the Soviets had very quickly developed a new variant of the T-72, designated the T-72M1 MBT.