Slapped on a SC onto my Z, never lost my warranty.
Had a transmission replaced with the SC on the car, steering lock, and other little items that broke.

Not explicitly true.

I've never heard of an OEM or aftermarket drivetrain warranty that allows it. If you know of one, I'd sure like to know whose it is (just in case, 'ya know).

Unless expressly excluded in the terms of the warranty and those terms are legal in the state where the the vehicle was purchased, then your SC is not automatically a valid reason for claim denial. If your SC can be reasonably linked to a part failure, then the claim can be denied. But that would be true of other mods, not just forced induction.

Got it. But trust me, the way it really works is that if your SC can be at all linked to a failure then the warranty claim will be denied. Isn't that how Nissan would handle it?

Can you fight it? Sure, but good luck with that (and I hope you have the money to afford a lawyer).

It's been that way for a long, long time.