Well, I can certainly tell you what I think of when I hear "DM decides."
I think "DM whim, which may or may not have any relationship whatsoever to anything the DM has previously said, anything that is mathematically sound, or anything that is entertaining for anyone besides the DM."
So many DMs who advocate for this style talk about DM trust. I never--ever--see them talking about trusting their players to be upstanding participants. Matter of fact, I find exactly the opposite; they frequently presume the worst of their players, expecting them to be manipulative, deceptive, malcontent, and disruptive unless firmly put in their place.
I find this asymmetry bitterly hilarious. Only one side can demand trust--and, incidentally, it's the side that has all the power. Only one side can question the motives of the other--and it's the side that controls nearly everything. Only one side can unilaterally declare whatever they want, whenever they want, for as long as they want, and change their mind on a moment's notice for any reason or no reason at all.
This all seems like a giant hyperbolic strawman. I trust my players unless proven otherwise, which sadly happens occasionally. I want the DM to make the final call whether I'm DMing or playing because it's worked for me and the people I play with for the past half century or so.
What do you even mean by "DMs don't trust players"? The rest? The DM declaring whatever they want, whenever they want? Complete and utter BS. At least for any DM that wants to maintain a group.