I haven't seen any articles about AMD PSP security vulnerabilities yet, but there's a new one about IME every other month. If Intel truly is the most secure in the world, why are their CPUs riddled with security bugs big enough to drive trains through (IME has de facto become a integral part of Intel CPUs) and where are the news about non-Intel CPUs with similar bugs?

No, but it does mean more secure than anything else, which is pretty doubtful. Competitors to x86 have always had an advantage as far as security goes; then there is the ME mess; and now we have this latest bug. Nobody expects perfection, but Intel is not "most secure in the world" by any stretch.

True, but no one claimed that. We are, however, claiming that Intel is not the most secure in the world.

This, prior issues as linked, Intel ME, tons of undocumented instructions—some which mess up the system—, etc.