How to use filter using where and .Site.Data?

Thanks, but it doesn’t return anything I’m afraid. See here:

I searched some more and found that the “Site.Data…” are technically maps — not arrays — which could explain why the where does not work… Pretty counter-intuitive, especially since range works fine. See:

Wouldn’t hugo want to support this feature? Maybe automagically map the maps into arrays when used together with where?