Maybe he figures he'll make somebody's team no matter what, so a major league guarantee was not that important. The bonus might have covered the difference between the minimum and some $1 million guaranteed deal that might have been out there. He is betting on his health to some degree, but guys coming off seasons that were decent in 2020 will all find jobs even if there is not much money out there.
DD will be judged on this, but one cannot say that he has not completely rebuilt the bullpen. Neris is the one big holdover from last opening day. We assume Romero and Brogdon will have larger roles but their stuff justifies it. Alvarado and Coonrod are new hard throwing arms. Bradley is better than anyone from last year. And the end of the bullpen might have competence from some combination of Kintzler, Hale, Rondon, and whoever does not make the rotation. Still worry about our situational lefties, but the hope is for someone like Romero to step forward.
I don't know if the bullpen is that good, but it is mostly new and has a shot at average.
Edit - reading a little more it seems Kintzler took $3 million and no guarantee from the Phillies as opposed to a much smaller guaranteed number from the Marlins. Assuming he makes the team and a couple of million more for a left-handed bat, the Phillies will be something like $10-$15 million below the luxury tax threshold. That is probably where they want to be. Save a little money. But DD really got them to spend another $10 million than they thought at the beginning of the season and most was spent on relative bargains with some upside.