I’m a little late to this, but this is false.

Apple is quite lenient when it comes to third party mods or tampering than most companies.

For example; if you’re in warranty and you have a third party display (I.e your display was replaced somewhere other than Apple) and your rear camera stopped working; they will fix that rear camera free of charge.

And should your fake display break during the repair process of that camera, then they will change it for an Apple display free of charge.

If they open a device and see that it’s been previously opened and there’s screws missing, they will replace the missing screws and continue with the repair.

The only times Apple will decline a repair is if the battery is third party or tampered with (safety) and of the logic board has been replaced, removed or tampered with (usually to do with fraudulent resellers).

Source: I fix things for the fruit company