On what specific basis do you assume he hasn't tried it? He's definitely blogged about the desktop apps, after all.
Or are you arguing that a writer doesn't have a meaningful or valid opinion on LLM-generated writing until they have tried to pass some off as their own?
This just seems weird to me. I mean, I have an opinion on this and I am personally never going to use an LLM to do published writing. On an intellectual level I can still see that there is nuance in it for others (for once I agree with him about an EU regulation).