I don't think it is accurate to call decompression models a "best guess". The models we used are all corelated with data taken from real human trials, and they are based on substantial investigation into decompression theory. While none are perfect, they are far from a "best guess".
I understand what you're saying. I was referring to things like this:
Richard Pyle Scuba & Rebreather Diving Physics and Fizzyology
If you ask a random, non-diving person on the street to explain what's really going on inside a diver's body that leads to decompression sickness, the answer is likely to be "I don't know".
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If, however, you seek out the world's most learned scholars on the subject of decompression and decompression sickness, the top 5 or 6 most knowledgeable and experienced individuals on the subject, the ones who really know what they are talking about; the answer to the question of what causes decompression sickness will invariably be: "I don't know".
2012 July « Doppler's Tech Diving Blog
According to the divers I know and respect, decompression theory is more fiction than fact, less science than art.
There was a poster here who quipped "Never assume an unexploded goat is evidence of a good decompression profile".