Well TBH COVID is part of your medical history so I don't think anyone needs to feel like you need to admit to your family and friends so long as you're staying away from them and for sure don't go out and about in the public while you're still considered contagious. As far as where you got it if contact tracing has determined it was from travel there ya go but otherwise it's still fairly difficult to pinpoint in most cases. TBH I'm always amazed when you read about events in the news where they've been able to do that robust contact tracing and pinpoint it down to the best of their ability. That's why whenever I read the cluster summary for my state (which now they give the locations and the names of those places) I take that with the dose of reality that the bulk of the cases are still not from identifiable clusters.
Contact tracers are a different story. Should you be forthright with a contact tracer? IMO Yes because they aren't there to judge. But I can understand how privacy concerns arise and other such things that make one not feel as comfortable disclosing. I know how delicate it's been when it comes to the protests for a contact tracers job. I would imagine that travel is the same.
At least they quarantined. They told their company (which sounds like they were supposed to based on your comment of needed to know) and they chose to quarantine. Sounds like a good example to me. It doesn't bother me personally if they didn't disclose to their family and friends. They stayed away from folks.
That was the point of the shaming thread. The intent of that thread wasn't that people were lying (which is what got the conversation going). That thread was supposed to be a spot where people could largely go for a less judgmental tone. FWIW I remember all the talk when Irma was going on. People sought out certain threads where they didn't get the whole "you're taking away gas and food and hotel space from Floridians how dare you, you're awful, etc" despite the fact that most of those posters didn't have a clue what the other posters plans were.
I don't doubt that someone has gotten it at some point there. I don't doubt that someone has gotten it from a grocery store either. But to answer your question I don't remember reading someone getting it from WDW here. Admittedly most of my threads haven't been about WDW travel at the moment other than seeing in passing people mention they still have trips planned, went on trips (and from what they wrote it went well) or just discussing WDW COVID procedures in general. It's also possible I read it but have forgotten