Then, yesterday, I finally understood:
It actually makes sense, if you think of the train as a "To Ogden" train instead of an "Ogden" or a "Northbound" train. But I honestly never understood it until yesterday.
My new understanding was confirmed by the voice at Salt Lake Central that afternoon:
Then, because I finally understood it, the announcement promptly changed. Today the voice said:
and I understood it immediately. It's amazing what a difference syntax makes.