SQ Mecha Overlord Great Magnas with 4 material, can be tributed by a Kaiju effect or its a bug? It happens with me today when i played with my friend?

Super Quantum Mecha Overlord Great Magnas

3 Level 12 monsters
This card gains effects based on the number of Xyz Materials with different names attached to it.
● 2 or more: Once per turn, during either player's turn: You can detach 1 Xyz Material from this card; shuffle 1 card on the field into the Deck.
4 or more: Unaffected by card effects, except by the effects of "Super Quantum" cards.
● 6 or more: Your opponent cannot add cards from their Deck to their hand by card effects.
If this card is sent to the Graveyard: You can Special Summon 3 "Super Quantum Mecha Beast" Xyz Monsters with different names from your Graveyard.
IT IS NOT a bug.

Tributing 1 monster your opponent controls is part of the procedure to Special Summon. so it is all OKAY.