That holds for boxing, but for more complex martial arts, it doesn't. Especially styles involving the legs.
As the Wiki itself says 'In mixed martial arts this may not apply, as having the more coordinated hand forward provides more coordination for blocking and grappling. A weakness of this strategy is that when facing disciplines like Muay Thai, which focuses on attacking the lead side - a person with their dominant arm and leg forward risks having his best weapons neutralized.'
Tifa is an arms and legs fighter, not a boxer. Southpaw stance for such would be to lead to the left.
You have a valid point WRT boxing, Fighter, and Edley, but we aren't talking boxing. That's my bone of contention.