Yes. But if they make a bold claim that "contamination can be ruled out", it's worth it to say to folks ready to take them for their word that, "it's still a possibility", even if it's not a testable finding but a suggestion.
Sure 'we can confidently say about every paper ever published that "I'm not so sure."'. But that doesn't mean we do say it for every paper ever published, or that we say it with equal weight.
The alternative is taking every research announcement at its word, and acting like it's true until it's taken down by another paper. And even then, why'd we trust the second paper refuting the first got it right?
In the end, it amounts to "if you didn't do the work or the review yourself, and din't find any specific actionable issue with it, then you should have no opinion about the probability of it being true or not".
Which is quite problematic. In the end, we often need and should be able to make a summary assessment of the possibility of a paper's conclusions being right or not (as based on our layman experience), even without working with the data, going through it with a fine comb or trying to replicate it, but based on a sense of probability of the conclusion, our knowledge of past assurances in similar statements being ultimately proven wrong, potential conflicts of interest, and so on.