If you wrote the file using the FileManager scripting approach, and then imported them into Devonthink, you could specify dates.
I’m not sure what you are doing with a URL scheme in this instance. Maybe you are attempting this on an iPhone with DTTG? But I doubt a URL scheme being used to pass on files would enable specifying dates for creating those files. However, if it did, it would be described in the Devonthink URL scheme documentation.