Users (such as miners) who had not recorded their seed words tried to backup their stealth address with
dumpwallet or dumpprivkey sv...

While attempting to dumpprivkey will clearly fail, giving the error message Address does not refer to a key (code -3) it may not be clear when using dumpwallet that private keys related to stealth addresses are not included.
Certainly, it would be futile to backup an endless list of keys used by a stealth address, and both the wallet.dat and the seed words are the only true backup, so maybe we can add some kind of warning to this effect when someone uses dumpwallet and in the help text for both dumpwallet and dumpprivkey.