The first query returns three values, without NULL:
If count is added, it claims there are 3 empty strings instead of 2.
The second query, plain SELECT without DISTINCT, hangs (subject to max_statement_time).
Reproducible with MyISAM and Aria. Not reproducible with InnoDB.
Reproducible with big5, utf8mb4, utf8mb3. Not reproducible with latin1. I didn't try other charsets.
Not reproducible without DESC index.