That's what IB like to hear and what they were hoping for. IB reminds me of 'made in China'. It works for a little while, the idea is to bin it after a year.
I don't know - it sure is odd. I was on the NYSE site for a few days doing some research. My broker told me I was flagged by the NYSE as a professional because of this. The claim made by the NYSE "only a professional would be looking at the type of data". I never had a Linkedin acct. The NYSE was fishing - they went after many clients for illogical things: like having a LLC, doesn't matter what it's for - according to them your should pay the pro fees if you have a LLC for selling beads. Any push back and they dropped it right away. Which clearly shows they were in the wrong & knew it.
I'm an IB-pm account holder in the US and in a very similar situation to you. They (IB) have not done this to me (so far) but Livevol did already. I did exactly as you did and countered their incorrect reclassification of me to professional using verifiable details. They simply would not accept this and so I can no longer use Livevol's option data which was a key part of my strategy generation process. Its damn hard to find affordable and reliable option data. Now I'm scared about IB.
One possibility is to describe at your LinkedIn introduction that you "used to be ..." or "formerly active as ..." or something like that. That indicates that that latest position/job/career is not applicable at the moment. This gives you the opportunity to decide at a later stage whether you actually want to delete that LinkedIn profile or not.