Perhaps there's a hidden mechanism that enables power after insertion? There was no switch for each outlet. I no longer remember if there was a switch for the pair of them but I don't think so as I was worried about getting shocked. This was in a Belgian hotel I visited a few years ago. Sorry I didn't take a picture.
This is probably the only case when CEE-style socket is not designed such that it is safe to use with any CEE-style plug that mechanically fits. In general I view the system as better design than BS 1363, because it solves the relevant safety issuess without overengineering and with reasonable degree of backward compatibility.
Outlets next to each other, still without cover: https://www.entscheider.com/elektriker-und-elektroniker/wp-c...
Maybe even like this (seems to be older): https://de.wikipedia.org/wiki/Schuko#/media/Datei:Doppelstec...
Definitely not normal what you describe there. I'm glad you were cautious.