Today I was at a the American Service Center in Alexandria, Virginia, getting some parts. This is a purely Mercedes place. I mentioned my frozen bolt technique to the parts person there.
He looked at me and said "You want to know what they do here? They use this stuff..." and he pulled out a can of Wurth Rost Off (I never heard of it before). "They swear by it."
Lo and behold - this stuff is the chiller and the penetrating oil combined! It's basically the same technique - it chills the bolt to -40 degrees Farenheit (not celsius), creating cracks in the bind.
So the good news is that what I did is fine and actually common practice among pros, the bad news is I was not the first one who came up with it!
Here is a link to the product...