I don't have a WaPo subscription, so I can't read the article, but I'll offer my thoughts. I kinda get where they're coming from, I guess I get where everyone comes from when it comes to restricting large gatherings (I personally am in favor of reducing large gatherings whenever possible) but I'm not surprised.
There are two angles that a journalist could have taken this story from:
1) Coronavirus rages on, but these guys are still finding ways to get it done. Inspring.
2) Coronavirus rages on through compromised town, and this large gathering of non-natives may make things worse. At the very least, raise questions about this. At the most, outrage from the community.
Both angles can be considered newsworthy. The logic behind option 2 would be raising skepticism behind the race's plans to contain the virus, which I think is reasonable. If it were me making the editorial decision with my running background and obvious bias, I'd say eh, go with option 1 -- I've read through the plans and it seems they are working with everyone's best intentions in mind. This is not structured like a "super-spreader" event that deserves greater criticism like that motorcycle rally a few months ago. And an ultramarathon of all things is probably way lower on the list of spreading concerns.
Now if I'm wrong and WaPo is right I also wouldn't be entirely shocked, but eh...