The same deck is in this context a deck that uses the same cards. You can't use two decks that use Lycanthropes, for instance.
So, in this context, and given the above quote, I have a question for clarity. Decks are for illustrative purposes only.
Round 1 Deck is :
and includes ONLY the aforementioned Lycanthropes, Steals, Fog Shields, and Quints. For this example it is fueled entirely by Quantum Pillars.
Your quote above indicates that I cannot use the same cards, and that is what indicates a deck distinction.
Does that mean that a Round 2 Deck could be:
and include ONLY Discords, Devourers, FFQ, and Lightning, also fueled entirely by Quantum Pillars?
Since the using the same card twice in a row is apparently the distinction, and all but Quantum Pillars belong to an element, not being able to use the same regular pillars/pendulums would be what held back using the same elements, but different cards, two rounds in a row. If the same decks were fueled by that elements pillars, they'd run afoul of the rules and not be legal, since they used the same cards from the same element twice.
Is this all correct?