Yeah, this one surprises a lot of people.
In the US, a standard king room is basically priced for two people by default. In a lot of Europe though, rates can genuinely be per person, even if there’s no breakfast included. It’s more of a property level thing than a global “Marriott policy.”
So the front desk saying it’s Marriott policy isn’t really accurate. It’s usually the hotel’s own pricing structure. Some EU properties absolutely charge extra for a second adult in the same bed, even if nothing changes about the room.
€20 per night isn’t unheard of over there, but it definitely feels odd if you’re used to US norms and you’ve stayed 400+ nights without seeing it.
If you’re curious, try a dummy booking on their website for 1 adult vs 2 adults on the same dates. Sometimes you’ll see the price difference baked in.
Annoying surprise, but not totally unusual in Europe.