I cant find the comment, but if I remember correct, that was from an real life experience from @ywwg.
The problem is that the query string itself may exceeds the limit due to the arg(trackIdList.join(",") call inside removeTracksFromPlaylistsInner.
The maximum number of bytes in the text of an SQL statement is limited to SQLITE_MAX_SQL_LENGTH which defaults to 1000000 (from http://www.sqlite.org/limits.html)  
As long we are unsure about the actual track limit, 255 will work in any case but does not hurt too much.