My friends iPhone got replaced 3 times, every single time the same fault. Something to do with audio interface going missing and mic not working.
His next phone was an Android.
I remember looking it up and there were rumours that Apple had initially acknowledged this fault and replaced them with no questions asked but then withdrawn the memo.
My Pixel 4XL, that I bought second hand, had it's battery replaced TWICE under warranty. Then, it started failing against, and I got an OS level alert saying they're detecting another battery fault and that I was eligible for a warranty extension at no cost, and to go and get it fixed. I just take it to the nearest UbreakIfix (or something like that) and they fix it in an hour sometimes, once it took a few hours because they were extra busy.
I was so impressed I bought my dad another used Pixel 4xl because I trusted them. And I'm someone that in general dislikes Google for losing their way the last 5-10 years.
Many faults like this are caused by some behaviour of your friend that none of Apples internal testers did.
For example, maybe your friend used a specific app that no tester every used.
I remember once a big company doing an emergency product recall because they hadn't tested putting the product in fleece lined pockets. If you put it in fleece lined pockets, it wouldn't boot anymore due to the static discharge of the fleece rubbing on the plastic surface as you walked around.
Yet they had 1000+ beta testers, yet were somehow unlucky that not a single one used fleece lined pockets!
His next phone was an Android.
I remember looking it up and there were rumours that Apple had initially acknowledged this fault and replaced them with no questions asked but then withdrawn the memo.