Why does the Spiders card require discarding two Determination tokens when Bats offers a choice?

Question

Accepted Answer

Bats lets you discard one Determination token or take a wound. Spiders requires two tokens; if you lack them, you take one or two wounds depending on how many you have.

Robinson Crusoe: Adventures on the Cursed Island

Why does the Spiders card require discarding two Determination tokens when Bats offers a choice?