Nothing to do with that. Car manufacturers will use the same engine in various variants of a car model. VW used a 2.0l diesel in the Golf for 1.8 and 2.0 versions. The ECU restricted the output and the service plans are built around the expected wear and tear of the engine based on the ECU performance. So if you remapped the ECU you add wear and tear to the engine the service plan and parts are not designed for, this reduced the lifetime of the engine and parts so the warranty is void.
Modifying the device so that the CPU is being operated outside the manufacturer's defaults adds wear and tear to the device and CPU, you affect the thermal output which may cause internal damage to the phone. So unlocking a device quite rightly voids the warranty as it can be used outside the agreed operating limits.
You're saying the exact same thing as I said already ... Lol. The onus is on the defendant to prove the modification caused the damage.
It has already been proven if a car's been modified to run outside of factory specs, that causes cause damage above and beyond normal wear and tear, thus voids the warranty.
Simply because a phone CAN be overclocked does not mean it has been. It also does not prove any damage has been caused by what one could POSSIBLY do.
By that same token, all warranty could be voided simply because you drink water and you COULD have spilled water on your device.
The onus is on the defendant to prove what actually caused the damage.