Apply some simple logic to that, please.
While being on 2.8m/year why would he refuse 5.5m/year last summer knowing that he will anyway be forced to stay for another year? That would mean he rather stay here 'against his will' for another year on 2.8m/year(which is half of what he could have earned in that same time span), renewing doesn't mean he coudn't eventually leave the very next summer afterall... Does that really make sense to you?
That being said, i don't believe even the slightest of that 'rumour', to me it's more likely that the rumoured 5.5m/year was rather what he demanded, and the club probably wasn't willing to match that.(but yet again all this are so far just assumptions, nothing more.)