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The truth about their current stated policies is more complex than what you have stated as your understanding of the policy. Here is the main window into the current policy:
Notice how first of all he is referencing the fact that there won't simply be 'the same set in a different color'. He mentions things like texture changes, recolors, and having individual pieces be incorporated into different armor sets. That is not equivalent to 'there's going to be the same costume but in a different color' by any stretch.
Texture is a huge part of what makes a costume feel a certain way. Layer on a complete change of context, that will almost certainly require minor tweaks to fit the sets over all presentation and you have a possibly radically different looking piece. He himself even states in this same post that 'it may be difficult to tell at a glance', so I am pretty sure he and I are on the same page in what he is saying here.
I would therefore argue that based off this core guidelines that no, 'obtainable variants' are neither guaranteed nor something you should expect. You
might
get something similar, you might get something radically different. Either way they get to rightfully try to sell you on the idea that a 'retextured, recolored, recontextualized and possibly tweaked version' is equivalent because it's a bad pr look to not do so and they've been very honest and transparent about their approach as stated above.
No one is arguing, on the other hand, that the best cosmetics won't be obtainable in game. He states that as part of his guiding policy. We have no real reason to disbelieve that. The community will speak out on release if it's not true, and it will be something that will gradually be fixed over time because there will be incentive to make that true. So for now I'll take Steven on his exact word. You know why? He's consistent.
Nothing here contradicts my assessment and only reinforces the exact points I am making.
Notice how here Toast is referring mostly to creatures, and how Steven has consistently mentioned NPC's as a major place you will see these 'alternatives', not exactly player obtainable versions of the sets. Because mobs and mounts are all one coherent 'skin', I think animal husbandry enthusiasts and mount lovers as whole will be the more obtainable 'color alt' scenario, but again that is still a might. So far I haven't really found quotes equivalent to this that support the same for armor and costumes, on the other hand.
I'll leave you with this last bit of footage
https://youtube.com/watch?v=JH-sX1aFljM&t=3509s
clip starts at time stamp and goes to 1:01:37
He makes it clear in this clip that his idea of how the shop will work down the line is that you will get something exclusive and that it and I quote "I want to incentivize purchase, by offering limited items; limited time, limited quantity. So that you have confidence when you purchase them they wont be offered later down in some other way." - Steven Sharif Pax East 2018
Even if these initial monthly cosmetics now have some alts, the policy in the long term is not just stated perfectly clear here, but in a lot of other quotes from Steven as well. The guiding principle, is the Steven sees cosmetics as something that shouldn't be repeated. Alt colors of a costume is definitely not what he means by 'equitable alternatives'.
So to me this is a person who has been very up front with his policy, and that leads me to believe he will go for the more radical shift of 'recontextualized, retextured, recolored' more often than not unless people put enough pressure on him to change his mind (which I don't even know is possible or not as he tends to not like changing approach or stances quite a lot.)
If that somehow still wasn't enough evidence for you, I welcome bringing more clips and evidence to the table here.