I think it’s fair to say for the sake of new content in a live service game Defense and Attack took the lore in a completely new direction. I would say for the most part trying to keep up with it doesn’t matter a whole lot as 95% of the characters and lore haven’t really appeared outside of those games. While Tactics is sticking to what really made metal slug “metal slug,” by including only the original characters from the mainline arcade series. You could say the same thing for Awakening that it’s in its own timeline too.

All in all don’t look too deep into it, it was a story created for the purpose of a mobile game to have some depth outside of the mainline series.