Why do some labs that do the etg/ets testing say that this type of test at the 100ng/ml cutoff and 25ng/ml cutoff say that:
EtG/EtS can not be masked by illnesses I.e. Urinary tract infections, and false positive results from diabetes are eliminated? Are they saying that this is a 100% accurate test and if you were to get a positive reading that it could only mean that you consumed acohol?

Not sure which lab(s) you are referring to. The vast majority of information provided by the commercial testing labs is no more than a sales pitch. If their pitch isn't referenced (to supporting studies) don't rely on it.

Some of the labs still claim that EtG is detectable only if alcohol has been consumed... rubbish. (See Link to Skipper previously provided)

Under a different post I provided you with a link to the Advisory issued by Health and Human Services. You need to read that as a start point.