Inconvenient Managed Properties: when strings are numbers
Recently I discussed this issue further with fellow SharePoint MVP and Search wizard Mikael Svenson. Eventually I’ve done one last test: ignoring the data type displayed in the Search REST API result I added sorting to the query. It turns out that sorting works just as expected after all! So even though the data type returned in the Search results is string, the sorting is performed using the integer data type.
So to recap: the standard RefinableXXXX Managed Properties display the correct data type in Search Schema, they return strings in search results, but when used for sorting they work just fine.