It's important to keep in mind who the person is. Reporters live on their credibility, so when a reporter like Windhorst says something he knows will be aggregated and doesn't throw in 3 disclaimers, aggregate we shall. It is also important to pay attention to the words he used (via The Jump):
It's not impossible for the Celtics to get their hands on Kevin Durant this offseason. I know that everybody's assuming that (it's gonna be New York). I'm not saying I think it's gonna happen, I just think it's possible.
So just to point out again, this is not him reporting from sources nor is he talking about this as a highly likely scenario. But we didn't see Kawhi in Toronto or Paul George resigning with OKC without the Lakers getting a meeting. There are surprised in player movement, and if there are two players that top the "most unpredictable" ranks, they are Kyrie and Durant.
Windhorst pointed out that the Celtics were in second place for signing KD the year he went to the Warriors, so there is respect for the organization there. His reasoning was that the assets they have prepared for AD would probably be enough for a sign-and-trade if KD was to express the desire to play with Kyrie in Boston.
Nichols mentioned Kyrie talked about KD as his "best friend" and there is a lot of rumors about the two of them and their free agency future. This is another concept floated out there and it will be interesting to see how meta can Kyrie get about this one. We all know how KD will react.
Honestly, I just hope they end up together on a team in a big market. Boston, New York, wherever it may be. The press conferences and reporters asking absurd questions such as "are you confident in your team" and "where have you been for the past nine days" with the two of them on the same team would be fascinating.