You probably can't. You can probably justify a lot of preconceptions about a person. But unless you've done statistical studies that demonstrate high correlation between what you're testing, what you think you're observing, and what you're actually looking for, then no - no you can't tell a lot.
Young male candidate, lets a big stack build up on one side, then clears the lot down with a couple of well-placed four-long blocks down the edge. Shows an easy confidence, clearly worth considering for the role.
Female candidate, lets a big stack build up on one side, what is she doing? Does she even know how this game works? Then she drops a four-long down the side and clears some rows. Huh - lucky break.
"Not that Tetris would be the only input into the decision, but it was a thing."
Hmm.