Yes that seems unlikely. Almost all Unix software uses buffered IO, including several other databases or database-like things including package managers, DNS servers, mail servers, ..., and MySQL does too by default. It even uses it when you choose O_DIRECT (though I'm not sure if that's exposed to write-back error eating risk or not).

That said, as several people have said, this is a very unlikely failure mode. When filesystems die, you know about it. The type of transient failure required to lose data this way is quite unlikely.

by reading the lwn article it seems postgresql is hit especially hard per its design and "heavy" use of fsync, I have yet to find similar impact on mysql.