I'm not sure how you can conclude that?It comes down to #3
Does his work require impartiality?
In football terms then yes it does.
On any other subject?
No, because it's not part of his job.
If he was a political correspondent then he would have to remain impartial
So he doesn't have to.
I am sure some of the top people in the BBC, who are fully aware of their own guidelines, had a lengthy meeting, and concluded he could not do what he did. I am sure this meeting included some top lawyers.
So, what do you know that none of them know?
The issue isn't really can he or can he not. It is how the BBC deal with it, knowing the attention it will get.
Liverpool could do with Lineker on penalties.