Can anybody think of what the difference would be in share sheets?

I’m a News+ subscriber, but the interface is abysmal - so I want a better way to track what I’ve read. If I pull the WSJ feed in NetNewsWire, the headlines all pop in. So far so good.

Now if I hit the “share” button in NetNewsWire, and use the “Open in News” share sheet, News tells me the story can’t be found. But if I first open it in Safari, and then from Safari use the exact same “Open in News” share sheet, it pops open in News just fine. I’ve had one or two work from NetNewsWire - but not the others. And using the NNW share extension to put the link into Mail or Messages yields a valid URL.

Can anybody think of what the difference could possibly be? Those share sheets are system-level, aren’t they?