ok, just watched so now i can give a proper response. although i will say, i have no clue where they're getting Gustav from, since in Minish Cap he's simply refered to as the legendary hero or hero of men. he was never named so where they get Gustav is a question i'd like answered.
now as for the theory: the most prominent one(which is what i believe) places Minish right before 4swords. its opening legend coming right after OoT, referencing the war Ganon waged. it makes perfect sense even within that theory as well because they even speak of this supposed war. all the legend really states is a hero defeated the evil with the 4sword, it never said anything else. this could mean that the evil resurfaced and attacked again. after the hero had died.
as for TP, the only thing i say they got wrong was placing it too close to WW. i'd say its like 10-20 years after OoT but still 50-90 years before WW.
technically none of this really matters because it still brings up a point i made earlier: what would his moves be because other then his sword, nothing is said of his powers or abilities.