I would.
10 years ago, no. Today? An audiofile is really easy to make with or even just a couple people in a studio.
It's also really easy for Greenblatt to issue a denial.
That is, of course, unless it is true.
A denial wouldnt necessarily indicate that it is false (he has every reason to deny it, but lying is a risk) but the lack of a denial is very strong evidence that it is, in fact, true.
There is a very low cost to denying lies, so the absence of a denial (unlike its presence) is a very good indicator.
"No rumour is true until it's categorically denied" -- Otto Von Bismarck.
> There is a very low cost to denying lies.
So people can just lie.
See: Clinton and Lewinski, the Profumo affair, Russian troop buildup on the Ukraine border 2022, Russian attacks on Ukraine 2014+, claims by NSA execs prior to the Snowden leaks, etc.