It just seems like a pure upside play for the Jazz, they can pay him next year and give him far more minutes and if it works out, they can keep him for two more years. If it doesn't the deal isn't guaranteed.
Of course the idea that it becomes more onerous for the Sixers if they make the second round next season seems doubly flawed right now, i.e. who knows what kind of season, with what players, they are actually going to have, and if they do make, it, and he's good, they can still afford him in the subsequent years, or he'll be tradeable.
I wouldn't say Reed wants to leave, but he doesn't want to stay for $2.6 million. And he also doesn't want to re-sign and then get thrown into a Harden, Tobias or deadline deal. But that, more than the $ and tax issues, is probably the best reason for the Sixers to pass on it.