mysql password as command line option

From the man page: 

--user=user_name, -u user_name 
--password[=password], -p[password] 

These work: 

-uuser_name -ppassword 
-u user_name -ppassword 

This does not: 

-u user_name -p password 

These work: 

--user user_name --password=password 
--user=user_name --password=password 

This does not: 

--user user_name --password password 

I see no reason why -u should accept an optional space prior to the argument and -p should not, nor why --user should allow a space instead of an equals, and --password should not.

original source: https://forums.mysql.com/read.php?10,229253