Reference for what, exactly? There are no references that highlight the issue of storage performance in iPhones. I haven’t even found a review that looks at storage performance of iPhones in the past three generations. Brand new performance, not even performance over write cycle. That is the issue I’m raising.

If you want a reference that proves that NAND performance degrades over write cycles: then I will only list one, but there are hundreds, at least.

https://doi.org/10.1109/RELPHY.2008.4558857