I did the test today, used a piece of walnut glued to maple. I deliberately applied too much glue so it would foam out of the joint so I could test that "free section" first.
I first used my MK heat gun and was very encouraged as the free section just sort of went gooey right away with very little heat.
Ha! This will be a cinch.
Not so - while that was very easily melted I went on to heat the 1/2" thick piece of walnut to separate the two pieces. Heated, and heated, and heated and.......
No go. Then I heated a thin putty knife with a torch, got the edge very hot, and tried to press it through a bit at a time without forcing it. Nope, not that way either.
As Phil said, I can do it with a very thin knife as I've done before, but the problem I was facing was in a situation where a thin knife cannot reach into the joint. So I was fortunate that I found another way for the repair in question.
I have melted epoxy before with only a part of the amount of heat applied to the Gorilla, and Titebond with the same amount of heat I used, but the big ole ape says not today, sucker!
Now we know.
Blessings,
Will