There was a lot of press about him wanting to test free agency. Only Mookie really knows how dedicated he was to it. I mean, it was obviously his best negotiation ploy, even if it wasn't his wish. (I still say he never should have made it through year five without an extension and it really should have been wrapped up much earlier, maybe in after his second or third year, the way teams like Atlanta and Tampa do it.)
But the general attitude is that "the player is always right" in these negotiations is simply not true. With Bogaerts and Lester, both received lowball offers and fan perception was they were insulted and correct to walk away. With Betts, he reportedly made extremely high demands, but the Sox were wrong to not negotiate? It has to work both ways...