It seems to me that we might just want to skip requesting auto-centering entirely with the SDL/evdev backend, as, like you said, the semantics of reset isn't to enable to disable autocenter and instead to reset the device to its default state (which is up to the driver).
For Proton (in Proton Experimental) I have implemented this as a per-device user-configurable option, do you think there is something wrong with this approach?