There are various opinions on Sue Gray. My missus for example thinks her investigation was a whitewash because lots of stuff just didn't get investigated. Those opinions are pretty baked in, regardless.
The other opinion at play here that is baked in is Partygate, it's what started the Tory Party's rapid descent to where they are in the polls today.
What the Tory Party don't need right now, is people being reminded of Partygate
And that's exactly how Labour are commenting on this today. "Everyone remembers Tories smuggling in suitcases of booze"
That's what people will be reminded of, not that it was Sue Gray's inquiry.