> TLDR, most modern tetris games, including tetris 99 select a permutation of the 7 unique pieces every 7 pieces; this means even though Tetris 99 shows you the next 6 pieces, you may know more about the next pieces.

Wait, is this true?

I always assumed each piece was selected perfectly randomly, making it possible (though rare) to get the same piece 3 times in a row.

If what you're saying is true, then that mean there should never be more than 12 pieces between I pieces, and if you get two in a row, then it'll be a minimum of 6 before you see another.

Which...all seems within the realm of possibility. Tetris always seemed really good at having a very even spread of pieces without "streaks".