Flipping "Majestic Mech "“ Ohka" or "Majestic Mech "“ Goryu" face-down will not reset their memory of how they were Summoned. So if you Normal Summoned them with fewer Tributes by using their effect, they will still be destroyed by their effect during the End Phase even if they have been flipped face-down since being Summoned. (However, as long as they are face-down DURING the End Phase, their effect will not activate during that End Phase.)
The effect of "Majestic Mech "“ Ohka" and "Majestic Mech "“ Goryu" that destroys itself will activate during the End Phase of every turn (if they were Normal Summoned with fewer Tributes by using their effect).
So, if I Normal Summon Ohka/Goryu with their effect, using less Tributes, AND I use an effect like Dimensionhole to remove it until the following turn, I still lose it?
It just seems at odds with the way similar effects, like Spirit monsters and Majestic Mech-Senku, work. How is that explained?
The effect of "Majestic Mech "“ Senku" that destroys itself only activates during the End Phase of the turn it was Summoned. If it manages to remain on the field longer than that, it will not destroy itself during any following End Phase.