In his defense, Sebastian confirms he is aware of those policies, but his argument is that Apple should still be obligated to repair the iMac Pro if he pays out-of-warranty fees.
Overall I agree with Sebastian, if technically—and per the terms Apple openly disclosed prior to purchase—they are under no obligation to service his iMac Pro.
In Sebastian's defense, it seems the customer friendly approach by Apple would obviously lie in denying the since excised warranty but nevertheless offer to attempt to fix (no guarantees, as tampered with) his computer on a time and parts basis.
Apple likely doesn't wish to set such a precedent, in only encouraging others into possible misadventures, but in the end such a policy only resulting in more repair work and income for them, not to mention the goodwill of customers with their baby now (likely) working again. This works fine as long as the terms of the warranty are clearly understood, AND that anything beyond what Apple sanctions is crossing the Rubicon. One takes their chances.
A couple other points. Being advised by the Genius Bar that one's new iMac Pro cannot be repaired due limited availability of parts seems disingenuous at best; if Apple's genius wasn't lying and otherwise making excuses then they would advise when they
could make said repair, with apologies.
The apology would be due (other than the part about lying) because Apple should not be selling a professional computer without the parts on hand to repair it, as for most professionals time is money.
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Addendum:
A common concern expressed questions Apple's liability in such a case, or how could they provide a warranty on such a repair without knowing the specifics of what another had done, or what might subsequently ensue after (many suggest a fire).
One solution seems simple enough: offer the repair and/or parts required but without any guarantees or warranty going forward—given the circumstances.