we highlight these issues in our docs explicitly.
https://pytorch-lightning.readthedocs.io/en/latest/tpu.html#...
https://pytorch-lightning.readthedocs.io/en/latest/tpu.html#...
I just read the linked page and found no references to data loading limitations or performance limitations. Is it only in the video which isn't search indexed and few people would bother watching?
edit: The page literally advertises the speed of TPUs with "In general, a single TPU is about as fast as 5 V100 GPUs!" which is the exact opposite of warning people.