The first time I noticed the Guardian repeatedly using words like "baseless" and "falsely" in news articles was around the time that Trump was alleging fraud in the US election. And I'm not sure but I think I recall the Guardian editorial team explaining that this was a deliberate decision to make sure they weren't unwittingly lending credence to his lies by reporting them.
Even back then it irritated me a bit. I agree that Trump was lying. But the thing is, readers are intelligent enough to make our own minds' up. To constantly be told that something is baseless and false is more than a little patronising.
Since then, this tactic has clearly expanded to other areas. And here I think the paper ought to be careful because if they cross the line and use the word "baseless" or "false" (in a news report, not an opinion piece) to describe an allegation that is debatable rather than 100% fiction, then not only will they alienate readers but they will lose credibility.