Apple has no chance to claim their batteries can have 80% capacity after 1000 cycles seeing how they never achieved this so far. Lying about it puts them in a world of mass recalls and fraud investigations.
I'm pretty the spec sheet claimed 1000 cycles when I bought my iPhone 17.
They do claim it at least for iPhone 15 "under ideal conditions": https://support.apple.com/en-us/101575
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Depends on how "cycle" is defined - I'm sure they can finagle it so "any charge added to the battery" counts as a cycle.
As a datapoint my iPhone reports 522 cycles and 89% max - from march 2024. I do use the "limit charging to 80%" feature which I suspect may become mandatory before 2027 ...