I think in that case it falls under mandatory warranty rules - if he didn't replace or reimburse them, he'd be liable. I don't know if warranty rules in the US are as strict as in Europe though. But in Europe, if your product is malfunctional within a year or three years (it's three for electronics, which is why warranty extensions from 1 to 3 years like AppleCare are dodgy), you as manufacturer are responsible for a replacement or compensation.
In Brazil it's 3 months for everything produced/sold here, electronics and complex stuff usually have a 1 year
warranty provided by the manufacturer (but by no means they are legally required to do that AFAIK/IANAL). Decent cars often have a 5 year warranty. I can't imagine trying to bootstrap a small business selling something in Europe and having to be extra super sure it is indestructible for at least 3 years or else I can be seen as some sort of criminal entrepreneur, it sounds scary... do you have any link or source on that for me to read?
EU Directive 1999/44/EC sets minimum of 2 years for consumer products, and requires that for at least the first 6 months the seller has to prove that the defect did not exist when they sold the product, afterwards it switches to the consumer. National law is allowed to specify longer periods, and does in some countries.
Note that it is the seller, not the manufacturer, on the hook for this.
