Hi Chancy,
The option on the print dialog and psk:JobPageOrder, even if related to each other, have different meanings. The latter is about printer capabilities/mechanics about printing, the former is about user preference on page ordering on the final printout, independently on which page the printer prints first.
GCP combines the two preferences together when deciding page streaming on the printer. For instance, let's consider a PWG-raster printer that has psk:Reverse set.
If the user leaves reverse option on the print dialog untouched (off), the pages are streamed to the printer in reverse order because the user expressed that the final printout will have the first page of the document on the first sheet of paper of the handout. On the other hand if the user selected reverse order then the pages are streamed in normal order, as the resulting printout will have the last page of the document on the first sheet of paper, as the user wanted.