The purpose of this is to support the annoying limitation that results must be a rectangular matrix. I tweeted this Oct 28th so clearly it solves a problem practitioners already agree with https://x.com/tomlarkworthy/status/1718329733274824783?s=20

Many useful result sets are not rectangular, trees, graphs etc. There is no way to efficiently transfer these results sets in a single query. You either do multiple round trips or pad the leaves with repeated information which eats network bandwidth.

So I am hugely in favour of this work.