Yeah but it's not just the grades but the idea of instantaneous cosmic travel, plus, from what I understand, some similar characters. It's the convergence of coincidences that makes it more unlikely. Also, apparently the DSC spore idea at first was very different, but it got changed after they changed showrunners.
The instantanious travel was possible without a tardigrade. They were never needed to make that happen. They were just needed to navigate the mycellion network and Bryan Fuller has documented interests in Stamets, Mushrooms, and Mycellium network prior to DSC.
So DSC could travel instantaneous WITHOUT a tardigrade and did. In his game, travel required a tardigrade to hug you to transport you
Where is the theft?