An unfortunate thing here in Portugal is that very often you learn your job by doing it, with the minimal training you get being in the bureaucratic process of doing stuff and no knowledge on the theory behind it, in this situation the laws behind.
So my guess in this situation is that if you’re from the EEA where documents are to a great extent standardized, they just insert all the data in the system like they usually do and it’s done, while if you’re from outside the EEA and bring all kinds of different IDs and paperwork they don’t know what to do and look at the actual law. Only then do they see you may need a tax representative etc.
As I mentioned in my previous post, art. 19 of the tax code makes no mention of nationality, only residency status, so if you gave them a Norwegian address, they definitely should have required you to have a tax representative.
There’s also the possibility that they knew that and just didn’t bother as it would give them more work (happens quite often) and in reality, the tax representative is just a formality if you’re not a company.
An example of that kind of mindset happened to me last summer when I went to renew my national ID card. After checking with me all my data was up to date the lady just asked me if I was still the same height as last time and as I said yes, we just moved on, when she should have taken my height in the machine that they have to do so. It was near closing time…