I think what this is all coming down to (as always) is a semantic difference. Nobody's actually really put a word or phrase to the thing we're discussing. We have "archetypal support," "spell diversity," and a lot of vague notions here. Let me try to explain what I'm talking about here. We'll call it the "archetype value" of a cube. Each card in the cube contributes some amount to each archetype accessible in the cube. Whirler Rogue, to use a favorite example, would contribute to the artifact archetype, the ETB archetype, the Reveillarketype, the sacrifice archetype, etc. You add up all the contributions from all the cards in the cube and you arrive at the cube's archetype value, which is expressed as a number of archetype and an "average support" for those archetypes. It's clear, now, that the way you draft the cube doesn't have any effect on its archetype value. In fact the cube has the same archetype value even if you never draft it, even if you just put a list of cards on a piece of paper. Increasing the number of cards always adds to the archetype value.
I think it's fair to use this (now more explicit) concept as a proxy for what the Mad Prophet was talking about. Notably, maximizing your cube's archetype value goes exactly hand in hand with the Prophet's suggestions to cut lands and fits with his grievances about lands taking up cube space that could be occupied by spells that help support other archetypes. It also suggests that you should cut lands or else build your mana base such that it contributes to the archetype value in some way. It's understandable that this wouldn't have been others' characterizations of what we were discussing, but it's the picture I had in mind and what motivated my claim that draft method does not add to your cube's support of various archetypes. A cube is a set of cards, not a collection of possible draft actions (i.e. grid drafting your cube doesn't make it a different cube)
Except archetype value, even as conceptualized here, is heavily conditioned based on % of cards you see in a given draft,
and the format you're drafting in. The former matters a lot more as your archetypes get more fringe, as Grillo noted, but there are also implications based on if the archetype cards are density/incrementally oriented vs big-payoff-oriented. e.g.,
/x Spells-Matter decks aren't too much of a problem to support in most Riptide lists, but getting 1
Monastery Swiftspear is a lousy reward for drafting lots of red spells if that's all you see because Prowess Beats is about density, whereas
Pyromancer's Goggles can be a big enough payoff that it's acceptable as the only
-based spells-matter pickup you make. And this is the most simple example I can come up with off the top of my head; most archetypes aren't this clear-cut. There's also questions to be answered about how strong a payoff is, and how desirable it is outside of its home deck;
Whirler Rogue is a great support card for a bunch of decks, sure, but how do you evaluate
Entomb? Does it get points for being a
Splendid Genesis and delirium enabler? What if you have no direct creature reanimation spells, but your cube heavily supports Welder strategies,
Spider Spawning, and
Burning Vengeance? How do you assign that point value? Cards are so heavily contextualized by what's native to their environment and how strong of a payoff you can get for running them. There's a million concerns which make "archetype value", as defined above, nearly useless without a million specific qualifiers. You could complicate the methodology, but you're probably best served evaluating archetype support from a different angle altogether than merely counting up where a card
could fit. I just don't think the "count em up" approach works when generalized to this extreme degree.
Draft method also has a
massive impact on the way a cube plays out, which anyone can attest to who has explored different methods than standard 8-person, 15 card packs, 3 packs each. You get very different decks and very different draft strategies out of Grid Drafting, Burn-4, Quilt, Lawyer, etc. We literally have people on this very forum, figuring out how you have to change a cube to take advantage of the unique opportunities and hurdles of grid drafting. It doesn't change what's in your cube, no, but it changes the % of cards seen and your ability to select freely from them, which it turn impacts archetype-oriented drafting.