Earlier quoted context omitted.
Basically, the announcement is a secret until it happens. It happens at a specific time, in Sweden, and they attempt to contact the winners at that time with a personal call ( https://www.nobelprize.org/prizes/themes/the-nobel-call/ ). My cynical side suggests it's done mostly to generate PR. See also: https://worldneurologyonline.com/article/receiving-the-call-... https://www.nytimes.com/interactive/2015/10/04/scien…
I think also due to their preference on making personal contact: the news will hit the PR landscape in short time afterwards and no soon-to-be-Nobel-laureate wants to find out in some news article
I understand saying that's a problem, but realistically, that's a problem very few people would be unhappy to have. Yes, it could be horribly inconvenient to stumble through a bunch of congratulatory communications before you could confirm you've actually won, but compared to wining a Nobel, it's a trifle.