In fact, 99.999999% is an extremely low estimate. The number of ways that a deck of cards can be shuffled is 52! Which is equal to 8065817517094387857166063685640376697528950544088327782400000000000 possibilities.
If you shuffled cards every second from the birth of the universe until now, you still wouldn’t even come close (statistically) to getting the same arrangement twice.
This is definitely mostly true.
It does breakdown some when every new deck has the same starting order, and people frequently shuffle poorly. Those 52! possibilities shrink massively.
I always think that when I see this fact - what counts as a shuffle? If I sloppily cut the deck once and reassemble, that’s most likely not unique. I wonder how many moves before a shuffle is statistically close to a random order. I’m guessing just a few, but I don’t really know.