I am not a split keyboard person.
But I have one big question -- why aren't the "middle" keys replicated on both sides of the keyboard? That is, for example, why not have two 'g' and 'h' keys? There are always times when you have to adapt; when you're holding down a tricky combination of alt-ctrl-shift keys or something where on a flat keyboard one would just reach with the "wrong" hand to hit a middle key; why not just replicate them?
If you want to do that, you can set many keyboards up to do exactly that. They just need to run the standard software - QMK, ZMK or Vial. You'll need to pick a keyboard with enough keys, of course, but there is plenty of choice. However there are other ways of solving the problem, e.g. a single key that is mapped to produce that combination. It's a matter of taste and experiment, and there is no reason for you to do it the same way as anyone else.
Then you would add more modifiers, not duplicate letters. Modifiers on holding homerow keys down (either side) are pretty common.
It's pretty common for Alice-style keyboards to have two Bs (the one in the pic in the article does) as on a normally-staggered keyboard the B key is basically equidistant from the home keys so it's common to use either.
But it would be a bit of a problem for keycap sets, some come with extra Bs to accomodate Alice keyboards, but none that I'm aware of have extra G/H/T/Y. That would mean you'd be into buying two sets or using weird keys, so it's probably unlikely to be a popular choice.
That said, there's so many custom keyboards out there, and it's easier than you think to design and build your own - if you feel strongly about it go for it.
I did have that problem a little when learning to type on a split, but I very quickly corrected after hitting the table a few times haha. I actually think it's arguably easier to learn to type on a split as it'll quickly force you to break some bad habits.