Just reminding

from the help

Chance spin

*If you receive a duplicate Level 100 card, it will be converted to an amount of Pero corresponding to the card's rarity.

Gacha

*If you receive a duplicate Level 100 card, it will automatically combine with a different card of the same rarity.
*On rare occasions, it will combine with a card of higher rarity.
*If all cards of the same rarity level are level 100, it will become a Wild Card of the same rarity.

So having full army of lvl 100 R isn't as easy as you said