You could absolutely have a recall pertinent to your vehicle that turns out to be voluntary and the automaker refuses to honor it if that system has been deactivated, tampered with, or modified.

Yeah, this could happen, but in most cases, you take your car to the dealership for recalls. And the dealer isn't the manufacturer, they don't care if you disable manufacturer shit. The dealer could get stinky and say no on the manufacturers behalf, but they would rather do the simple work and get paid for it, then try to upsell you on preventive maintenance like an oil change, tires, etc.. Unless you're doing something that'll come back to them (like odometer fraud), they're not gonna go out of their way (and spend 5x the time) to deny a recall claim that even the manufacturer doesn't give a shit about paying. That was my experience anyway.