True, it does not disprove Sasquatch - but it also does nothing to support it.
And on that "Absence of evidence is not evidence of absence" thing, that is in fact an informal fallacy. Absence of evidence (if you have actively been seeking to collect evidence with tools capable of doing so) absolutely is evidence, but not "proof", of absence in every branch of science.
If you go to a doctor and get a biopsy looking for cancer, and no cells are found, that is absolutely a valid indicator that cancer of they type being screened for, is not present (though the tests can fail sometimes to detect it when it is).
Environmental DNA/RNA sampling is a very powerful technique to detect the presence of species that are difficult to observe. Almost any physical remain left by an animal, even extremely small samples (feces, blood, saliva, hair, skin, tooth, nail, etc.) will allow detection of its DNA to be matched against libraries to determine its phylogenetic grouping, and species identity if known.
If over a reasonable amount of time no one can produce a sample bearing the DNA of a novel creature, then it cannot reasonably be supposed to exist.