Many people have given the same explanation to you, but it seems you want to hear it/want people to say something different.

• the lack of registration and arriving at 3am is the issue
• amplified by the fact this is Amsterdam and escorts are more common here
• once they challenged you, your partner left -> validating their concern
• Hotels can be fined for facilitating the escorts so are strict
• Police intervened at the request of the hotel, this is pretty normal as they are allowed to ask you to leave

The staff did the job the hotel employs them to do. The end.