Theres no reliable way to 1HKO the Ultra Necrozma, thus by targeting it, you guarantee that you will 2 shot, and within that 2 shot, they will likely get 2 Prizes, but not 4
Beyond that, signatures can be exceptionally difficult to authenticate and an unknown signature can basically make a card worthless
For example, In addition to these archetype-specific cards, each two-color pair has multiple signpost uncommons
You can simply treat it as a standard single-effect enchantment or a reusable sorcery, never having to bother with its transformation requirement ever
Additionally, consider purchasing from trusted sellers and checking the card's condition before finalizing your purchase.
Its subtle enough that many people dont see it immediately, but Wizards of the Coast decided it wasnt worth the risk for a card primarily aimed at children