I’m a little shocked at hearing that a stainless steel automatic is wearing out. Cops don’t typically put a lot of rounds through a gun. Handguns are kind of like motorcycles - they don’t die from use - they die from neglect.
We do not know how true the “wearing out” part is.
Maybe they just wanted to carry a much lighter gun.
The 5906 is an excellent pistol, but it is heavy compared to the Glock.