This would make no sense. They could have done a salary dump yesterday, accepted the best of the bad offers, and be free of the buyout amount and the rest of his prorated salary.
It isn't rocket science. Robert will make $20 mil next year. Robert (on the open market) or his replacement would probably cost the team 50-75% of that amount. It wasn't worth it to the team to accept a subpar package if they think they can trade him next year for something worthwhile by spending only an additional $5-7 million.
The only way they don't pick up the option is if he completely embarrasses himself or has some catastrophic injury before the end of the season.
If they just wanted to save money, they could have dumped him 24 hours ago and people would have been cool with that.