As far as I remember, it was Roy Thomas who first mentioned it in the mid-70s. And it's certainly possible that it was more subconscious than deliberate on Stan and Jack's part, but the powers do line up pretty well: Reed was reaching for the stars, Sue has her protective instincts, Johnny is the hothead, and Ben is a big lug.
Reed's the smart guy. The big brain. Getting to the stars is just one project, not who he is. The phrase works a metaphor for his intelligence, but not his shapshifting/malleability. Sue's force field is a later addition, not her original power. Turning invisible doesn't say protective in that sense. It says stealth or supernatural or even scared.. Johnny isn't really a hot head. He the smartass. The practical joker. Ben's more prone to losing his temper than than Johnny. Ben might be the only one were his personality translates to his powers. He's a tough guy who became literally tougher.
The metaphor only applies to one aspect of their personalities. Thomas also took it a step further in an issue of
What If? where he gave them different powers based on other aspects. Reed turned into a disembodied brain for obvious reasons, Sue got the stretching powers for reasons I forget, Johnny turned into a mechanical man because of his car hobby, and Ben gained wings because he was a pilot. The original configuration, though, has the added strength of its parallel with the four elements of antiquity.
So it's long past time people just admitted that this is normal now. There's no going back to the unjustly white-dominated casts of comics from the '40s and the '60s. This will be the way it happens for the rest of our lives, and it should be, because whites have already had their turn in the sandbox and it's long past time everyone got to play. So there's no point in making an issue about it anymore, because it's not going away, any more than women's suffrage or school desegregation or gay marriage is going away. There comes a time when you just have to face the fact that the debate is over and one side won.
What's really disingenuous is continuing to pretend that people who want to see faithfulness to source material are racists who want to go back to "white-dominated casts" and who are on "the other side." You've been told this before, but you're so desperate to be seen as an Enlightened White Male that you refuse to listen. Your self-righteous posturing doesn't impress anyone; it just alienates them.