Okay, to throw a wrench in this- how do you think the new formulations of thinner ("Safe thinner, I wouldn't call them solvents) affect all of this? In my experience, the original formulations of solvents/thinners were pretty predictable in how they reacted with "Tung oil" and other oils, but the new formulations, courtesy of our friends in California, are just a pain to work with and in my experience pretty unpredictable in how they react with finishes. Now, try to find the "original formulation" thinners these days...
The other thing is, what lots of guys are calling Tung Oil may or may not be actual Tung oil unless you can determine it's chemical content from the label, if the manufacturer is generous enough to supply one. Most of the cans marked Tung oil these days are filled with a synthetic material that is definitely not plant or animal based. This can also cause difficulty with predicting how materials will react with solvents and other materials called thinners...
Bob
CA did some ridiculous things based on a couple major advances they claimed could be duplicated... they were very wrong. Last I looked their limit on VOCs is 3% and that started about 5 years ago. Just shortly before that it had been 30%. The 30% goal had been reached by major advances and with nothing else on the horizon they demanded an order of magnitude reduction. They have placed a ridiculous burden on the industry and so far, they have failed to make anything resembling a user-friendly finish. I suspect there are a significant number of folks using non-CA finishes there simply because they have to to stay viable.
