if your board already has three creatures, and you fulfill an end-of-turn Descend condition that creates a token creature, you are forced to replace one of your creatures with a token. every other method of generating token creatures allows you to choose to not create a token, so you don't have to replace one of your good creatures with a 1/1 token
method: have three creatures on the board, and a Descend-based source of token generation. example: any two creatures and Broodrage Mycoid. match the Descend support and end turn with three creatures on the board expected result: Broodrage Mycoid triggers, creating a 1/1 Fungus token. popup allows player to choose a creature to replace, or to not create the token by selecting "Not Now" actual result: Broodrage Mycoid triggers, creating a 1/1 Fungus token. there is no "Not Now" button, and player is forced to replace a creature