kept as a bargaining chip

That's my suspicion too. Cutting all ties also cuts all talks. Norges Bank has a duty to their own investors to balance the financial interest with ethical principles. If they're otherwise profitable, it makes sense to hold on to the shares and use them as diplomatic leverage instead.

Not all activism needs to be cut-and-dry. Often, negotiations can move a lot more than pure antagonism (though they often need to be backed up by some "otherwise..." to hold any weight).