IF a fuel injector fails, they would have to PROVE the tune caused it to fail. Again, nothing is automatic. Consumers are protected by law.
This varies state to state. No one is guaranteed a warranty covered replacement. Ford warranty, just like any other company, has a list of stipulations they can pull from to “void” a warranty for components.
I have had tunes on several cars, most good tuning shops actually have their own warranty coverage too.
Occasionally a tune will push some components too far and fail prematurely, it does happen.
You should not expect those to be covered by warranty. If the tune is unrelated to the part in question. Such as Sync4 screen, or power seat control, those components are unrelated and likely won’t even come up in conversation around a tune for engine.
Using a different example, if you have an aftermarket shop sand and paint part of your hood and it rusts 12 m later, ford will not cover that paint under the warranty.
If you tow a 20k lb trailer and you blow a transmission, they will easily void your warranty.