Shifty Eyes

Both are part of 14 eyes, I’d be wary.

https://cyberinsider.com/5-eyes-9-eyes-14-eyes/

Its possible some wires got crossed behind scenes, some database/software mixup.

Maybe email proton support if you’re concerned? I’ve had some similar mixup happen with banking and they got it all sorted after I complained (I was getting emails intended for someone else).

Edit: either way, I think you should let them know in case its phishing or something broken on their end.

That is their official email address. Did you make an Alias or something and you forgot?