REST datasource filter set search not working

That being said, it still seems like there’s some kind of product issue at play here.

Why does merge syntax like this
{{#kind}}+AND+kind={{kind}}{{/kind}}
work for a filter in the data source url, but the exact same type of syntax doesn’t work for a search term supplied through the same filter set?

If I try to drop the merge syntax for the filters, the query fails! If I include the merge syntax for the search term, the query fails!

Why is there a difference?