This infinite list of letters could be "any random combination of letters EXCEPT when that makes the word “banana”. A subset of an infinite set can still be infinite.

Infinite != infinite randomness

So far, they are training models extremely efficiently while having US gatekeeping their GPUs and doing everything they can to slow their progress. Any innovation in having efficient models to operate and train is great for accessibility of the technology and to reduce the environment impacts of this (so far) very wasteful tech.