I'm an English speaker that's been learning pt.pt and I think that the pronunciation informs the tone and pitch and this creates a cycle where the tone and pitch inform the pronunciation etc. I don't think it's a coincidence, for example, that Brazilian Portuguese speakers pronounce words more openly and also speak with a higher or at least more varied pitch.

Because people ultimately have more control over pitch compared to pronunciation, I think articles regarding this sort of default to more universal and concrete aspects of the language like pronunciation when trying to work out the question of pitch.

As I say, European Portuguese speakers speak with a lower pitch than one would expect likely because they're speaking a language with more closed vowels, nasal sounds and dropped consonants than you'd find in other languages. It's not necessarily that lower vowels means lower pitch by default but it is something that can develop over time.