I flew from Athens to Stockholm today. At Stockholm airport everyone had to go through passport control. For the first time I was asked a lot of questions and I even had to show my flight out of Schengen. They were very nice but that just surprised me.
No, Sweden is still very much part of the Schengen area.
There are a number of reasons why you had to go through immigration, but while Schengen means that regular passport checks are abolished there might still be random checks so you might just have ended up in a random check. They might be a bit more common now due to the war in Ukraine. Or your flight arrived at a non-Schengen gate for some reason, that can happen, especially if you are flying a low cost airline. So any time you spend here will be part of your 90 days I'm afraid.
Also, did you catch the changing of the guards today? It was the first mounted parade since before the pandemic.
As part of the treaty, individual countries have the right to reimpose border checks for limited of time for any reason. It's happened to me twice, once on arriving in France from Switzerland during the week of national elections. Another entering Switzerland from Italy when the Davos summit was on-going.
I know Sweden didn't leave Schengen. I was being facetious. I think the reason they stopped our flight was because we were from Athens and they're lookingp for people trying to sneak n to the country.
The gate agents at the Athens airport were scrutinizing a few people's passports very seriously.