That there is not room to make both of them full-width is fine. But rather than make one full-width and the other half, clearly they should both be three-quarters width, like the Tab key or right Option key. Or just make them both half-width. Anything so long as they’re the same size.
I think Gruber is almost dead wrong here. On iPad, loads of text editing apps auto-close the right bracket once you hit the left bracket. This is especially the case in apps like Obsidian, or Notion, or Roam Research — double-press that left square bracket key and the other two right brackets auto-fill, or the UI gives you a picker to link your notes.
I think the key sizing on the Magic Keyboard makes perfect sense. I’d like symmetry too, but the current choice is more usable.
Do read the rest of Gruber's review of the 2022 iPads, though. I truly appreciate his caliber of writing, even if I disagree with 95% of the things he says.