If water-damaged boards are not worthy of rework and repair, then what is? Crushed or shattered PCBs? Torched battery units? I buy exclusively refurbished st

If water-damaged boards are not worthy of rework and repair, then what is? Crushed or shattered PCBs? Torched battery units? I buy exclusively refurbished stuff from Apple. Never had to use the 1-year warranty (which comes free with every refurb), but I sleep better knowing it's there. If a reworked unit doesn't crap out at Apple's bench test, and it doesn't crap out after a year of use, and you save 10-20% off retail, what exactly is the issue?