Result differs with DESC index upon comparison of timestamp with incompatible value

create or replace table t (a timestamp);

insert into t values ('2021-12-12 01:02:12'),('0000-00-00 00:00:00');

select MIN(a) FROM t WHERE a = '0';

alter table t add index ind(a);

select MIN(a) FROM t WHERE a = '0';

alter table t drop index ind, add index ind_desc(a desc);

select MIN(a) FROM t WHERE a = '0';

# Cleanup

drop table t;

select MIN(a) FROM t WHERE a = '0';

MIN(a)

0000-00-00 00:00:00

Warnings:

Warning	1292	Incorrect datetime value: '0'

Warning	1292	Truncated incorrect datetime value: '0'

select MIN(a) FROM t WHERE a = '0';

MIN(a)

0000-00-00 00:00:00

Warnings:

Warning	1292	Incorrect datetime value: '0'

select MIN(a) FROM t WHERE a = '0';

MIN(a)

NULL

Warnings:

Warning	1292	Incorrect datetime value: '0'

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra

1	SIMPLE	t	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where

Warnings:

Warning	1292	Incorrect datetime value: '0'

Note	1003	select min(`test`.`t`.`a`) AS `MIN(a)` from `test`.`t` where `test`.`t`.`a` = '0'

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra

1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away

Warnings:

Warning	1292	Incorrect datetime value: '0'

Note	1003	select min(`test`.`t`.`a`) AS `MIN(a)` from `test`.`t` where `test`.`t`.`a` = '0'

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra

1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables

Warnings:

Warning	1292	Incorrect datetime value: '0'

Note	1003	select min('0000-00-00 00:00:00') AS `MIN(a)` from `test`.`t` where 0