>reboot to bootloader -> unlock -> you will use your warranty -> yes
It's fucking outrageous that companies are allowed to blatantly lie like that (you will not, in fact, lose your warranty -- Federal law doesn't allow it). Every company that displays such a fraudulent message ought to be fined by the FTC, or worse.
By its nature, the only penalties that can be applied to a corporate entity are fines or revoking its charter. The latter is what I had in mind when I wrote "or worse," although I suppose piercing the corporate veil and going after the company's executives personally is certainly an option too!
It's insane to respect corporations' rights when we know very well how pointless they are for the public's interests. We want proper behavior and serious punishments. We don't want to respect corporate and their rights.
You can pierce the corporate veil. "What lawyer approved it? Who was responsible for putting that message there?”.
The corporation might not be able to be punished, but the actual people who did the thing can be.
The corporate veil for legal action only makes sense for a limited number of things that are problematic for the company but no person could really be expected to have directly made the choice.
OP is most certainly from a German speaking country based on the fact they wrote deinstall instead of uninstall, which is a false friend of the German word 'deinstallieren'.
The TL;DR of the Magnuson-Moss Warranty Act is that if the manufacturer wants to deny your warranty claim, the burden is on them to prove that the owner's "unreasonable use" (abuse), neglect of required maintenance, or modification of the product was the actual cause of the failure.
For example, a car manufacturer can't use the fact that you tinted the windows as an excuse to deny your claim for an engine failure, but they could deny it for your failure to perform oil changes.
Unfortunately the TOS you agreed to says a ridiculous "arbitration" will determine who's right that you abused the equipment - and guess who the arbitrator will decide for.
I've heard that from a lot of people, but never seen it in action. Someone who sues or somehow gets what they want in spite of arbitration, I'd like to see that.
Edit: Side note for consumers: Some US states have something called "implied warranty" laws that extend the warranty period of almost ANY product you buy -- even online -- usually for up to 4 years, and some states also extend it to used products as well.