Partner's National insurance number for Housing benefit

Hi everyone,

I hope I am posting this in the right forum... (I am very new in here).

My husband received a letter from our council which asked him to provide my national insurance number.
I have never applied one because I am caring someone full time and I am not able to work.
Also I am staying in UK with Leave to remain, so I cannot claim any benefit.

I went to the council office and they took my statement about m situation.
I showed my visa at the desk, but they didn't take a photocopy.

He received a second letter which says they have suspended his housing benefit and they applied for my national insurance number.
I found an information in 4 of Housing benefit regulations 2006 which says a subject to immigration control (which I am) is an exception to the requirement for the partner to provide a national insurance number.

I went to the council with this information and they took a photocopy of my visa this time.

I was asked to attend an interview for national insurance number with DWP, but I was not sure I had to attend. I thought if I am an exception to the requirement to provide a national insurance number, I wouldn't need to apply. And I have already provided a proof to be exception (my visa shows I am a subject to immigration control).

I asked the council and DWP but they couldn't give me a clear anser and suggested me to explain the situation at the interview.
So I went to the interview, but there was no way to explain anything there. The interviewer kept saying his job is only filling in the application.

The council says they will cancel the suspension of the benefit if they refuse to give me a national insurance number because of my immigration status.

I am still wondering if I had to attend to the interview to get a refusal letter.
As the regulation says, I no need to provide my national insurance number so why I had to try to get one even if I have no reason for it (not being able to work and no recourse to public fund.).

It's all done now but if I didn't need to attend, I would like to inform them because I got really nasty treatment at the interview (almost insulting) and gave all my personal detail there.
Does anyone know what was the correct procedure for this situation?

Thank you for reading a rather long post.