It would be an interesting experiment for sure to see if one could "terraform" Mars with some kind of life from Earth. But I don't see how it would be any more

It would be an interesting experiment for sure to see if one could "terraform" Mars with some kind of life from Earth. But I don't see how it would be any more actionable than any discovery of past life. Both experiments will give greater insight into theories like abiogenesis and panspermia, but that's about it. Better to exhaust the first before trying the second, since you can't undo the second one. Also a bit more scientific rigour than just seeing what happens to piggyback on the spacecraft would probably be warranted.