I love my Tempo Oil boy, but would never consider using it for getting an oil sample.
I don't think you can keep one clean enough to avoid skewing your sample. It is much better to sample when you drain and catch it mid-stream...kinda like a urine sample
One thing I have learned in 25 years of laboratory chemistry and chemical industry work is the value of a good sample. I believe you will have a tough time getting a good sample out of a used oil extractor.
Tim