OT. Two moons

Speaking of moons, there is some speculation that we originally had 2 moons , back when our "main" moon was formed by a collision with a Mars-sized objec t.

It is generally accepted that our moon was formed by chunks of material tha t flew off into space after the collision and then coalesced into our moon. There are some that now believe that 2 moons were formed in that manner and that sometime afterwards the 2 moons became one.

The theory goes that there was a low-impact collision between the 2 moons o n the far side of our moon. This low-impact collision essentially spread the material from the smaller moon across the surface of the larger one. This would account for the thicker crust and less evidence of volcanic action on the far side. The thicker crust would prevent smaller collisions from disturbing the surface "deeply" which would limit the amount of magma that could escape.

formatting link

Note: The article sited above discounts that theory in a manner that I feel is contradictory. Follow my logic here:

First they say that the original "collision then coalesce" theory related to our moon makes sense because "It explains why the Moon has some chemical s similar to Earth".

Then, when they introduce the 2 moon theory, they say: "...a smaller moon also coalesced out of the ejected material" which implies that the 2nd moon also had "some chemicals similar to Earth".

OK, so with that background, how can they discount the "absorption" of the smaller moon by the larger one by saying "The chemical composition of the lunar surface doesn?t have a sharp transition between the far and n ear side as you?d expect from this."

Why would I expect that 2 moons that coalesced from the same Earth material would produce a "sharp transition" in the "chemical composition" when compa red to each other?