I think it's still actually lying though. In GTA V, setting zero deadzone is seriously zero deadzone, you can get the crosshairs to move slightly just by tilting the controller ever so slightly, and it's not uncommon to have a bit of jitter even when not touching the stick at all.
In RDR2 it still feels like there's still plenty of deadzone built in there, even with it set to zero in the settings. But yeah, zero is a must.