Copyright does not protect game mechanics and rules. In
Tetris v. Xio, they successfully argued that the game infringed on trade dress.
They claimed that the pieces looked like ones in other games, which in my view is impossible not to infringe on since there have been hundreds of Tetris games with every type of piece design possible.
They claimed that they used tetrominos, and the playfield was twice as high as it was wide, and so on. What Xio failed to point out was that all of these are functional aspects of the game, which means it is not protected by trade dress. Even the original creator, Alexey Pajitnov, has said that he originally tried pentomonoes, but that was too difficult, so he used tetrominos instead. That's functional, not trade dress.
Do you have a source for Tetris's trademarking tetrominos? Perhaps you're referring to their "tetrimino" label, which their own term for what the non-branded world refers to as "tetrominos."
