Catastrophic engine failure 13 miles after an oil change

We have had a catastrophic engine failure 13 miles after an oil change.
What we know is the oil level is about 3 inches too high.
It is difficult to truly determine what the level is with this cable style of dip stick.
Oil change facility claims oil level correct when it left their site.
Only five of 12 quarts of our parasynthetic oil were returned to us.
The oil has a very dirty look to it.
Several rocker arms are broken.
The valves are hitting the pistons.
There is much play in the timing chain.
We have ordered a spectrum analysis sample kit from the parasynthetic oil manufacturer.
We will be draining, measuring, and analyzing the engine oil contents in a few days.
We are trying to determine if the timing chain guides failed coincidentally with the oil change or if the oil change involving a massive amount of extra oil is to blame.
It appears that no seals have failed.
The oil change facility claims that only possible failure from over filling an engine is a seal failure.
The mechanic is saying that over filling the oil to this extent is to blame.
Based upon what research I've done, I'm having trouble with both ideas.
I was referred to this site by a GM customer service supervisor.