Nobody is saying that they are. They are saying, however, that this is a serious about-face from what Elon has claimed in the past. He rode into twitter on a high horse and has walked back pretty much everything he's said since.
Because it's public information that's literally broadcast to anyone listening by every aircraft above a certain size/speed. This isn't information that is considered secret or even that one needs to dig to expose, the aircraft is actively transmitting regular messages containing its location, heading, and speed to anyone within radio range which can be tens or hundreds of miles depending on altitude.
Rather like Keir Starmer and the UK Labour Party.
Starmer is leader of the opposition party in the UK, he was elected leader by Labour party members after making ten pledges, all quite socialist / left wing, but since becoming leader he's basically reversed every previous position he's claimed to have and is now taking centrist and even right of centre positions - upsetting many who voted for him (while others, though not me, say it's needed to attract more center/right votes in the next election).