They barely address the why, skipping over any serious detail with a comment about "designs that weren't practical before"

And there's no discussion whatsoever about whether the negative impact on the mental model necessary for understanding Excel is worth the benefit for the unlocked cases.

I don't see why you can't just represent the cases with the existing structures and deal with that cost in cases that need it, because it keeps a simple mental model. Arrays are one of those things that mess with the simplicity here too - I'm sure there are plenty of hardcore Excel fans who find them trivial and/or essential but they're never intuitive and lead to all sorts of mistakes/delays if your spreadsheet is used by less expert types.

Keeping it simple seems a better direction in general.