The paper doesn’t seem to show perplexity for completions of a large dataset, i.e. the standard benchmark of language models. It shows benefits for specialized tasks, but as I said, specialized task training isn’t the goal. It’s always possible to outperform a general model by choosing a sufficiently specialized task.
I don’t know why people feel so strongly that the tokenization is a weakness, but ultimately there’s not much choice but to agree to disagree.