For more context, that's a comment from one of the ext4 main authors, Ted Ts'o. the other subsequent comment from him spells out the case more but sadly no spelled out NUL byte origin story I spotted from skimming.
The original report [0] shows the corruption due to NUL bytes at the end of the file (see the hexdump).
This comment [1] from Ted Ts'o details the exact chain of events leading to it.
