It’s because the properties are stored in a set when they are page references instead of plain text.
So to query for them we have to use contains.
This works no matter the number of page references.
[(contains? ?type "Project")]
https://clojuredocs.org/clojure.core/contains_q#example-542692cdc026201cdc326d2f
This is what is in the data, btw.
:block/properties {:type #{"Project" "eBook"}, :status "Active"}