I also don't really see what the enemy from Samus' past line has to do with anything, either.
Sure, Ridley is Samus' most prominent enemy from her past, but he's not the only one. There's still characters like Phantoon and Nightmare, both of whom also appeared in Other M. Heck, maybe even Kraid, who knows?
And before anyone mentions "Oh, but that's where you fight Ridley in Other M, so it must be him", may I remind you that Smash doesn't exactly follow canon with its hazards? Cresselia is a hazard on Spear Pillar, where it never appears, Big Blue and Mute City still have the Blue Falcon on them if Captain Falcon is being used, Milotic appears as a hazard on N's Castle, and Yellow Devil wasn't in Mega Man 2, the game that Wily's Castle is based off of.
With that, I'm done with the topic.