they are signing him now because of NBA offseason rules. they'd have to wait until a certain time to even talk to him, if it was over the summer. plus other teams could work him out, or he work himself out, and get himself signed somewhere else
also it's to do with the contract.. since technically he's signed this year, they don't have to guarantee his contract for next year.. they can literally sign him for the minimum of this "year", then he's offiicially on the roster to work out, train, see where he's at by next year... and if he isn't any good, they can cut him without paying him for the next season
phil bout to show y'all how to do this shyt with sneaky moves and manipulating the system!!