I have always found oil sampling results interesting. I have worked in an oil sampling lab for a short time. I used oil sampling at work for years (heavy equipment).

I think we need to temper the expectations of what oil sampling does and doesn't do. It tells you little about the condition of your oil. It can tell you a lot about the rate of wear of internal engine components, if done regularly and tracked/trended. One result tells you practically nothing. The interpretation is nearly always to change the fluid, and test again.

Yes, you can see if a sample has water in it, and what the TBN is, from one sample. But people always look to the wear metals, as if that is contamination. It is simply an indication of how fast things are wearing, and isn't an absolute metric.

The challenge I have had with Blackstone results is their frequent comparison to universal averages. They have so few data points of the same engine/application/specific fluid in their database that a universal average is very universal.

Transmission fluid testing is a whole other issue. Manual transmissions aren't an issue, it is cheaper to change the fluid than to sample it. Automatic transmissions don't get analyzed for what is important in a transmission fluid, the friction modifiers that impact clutch engagement.

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