Partial Payment of Drop Ship Receipt is it possible?

Good Morning All!
My Finance crew is trying to partially pay a drop ship receipt on a Logged AP invoice. The Final Invoice check box is grayed out. I can change the qty being receieved but it still closes the receipt. I have the Partial invoicing on in the company config but I m thinking that its only meant for regular receipts. Am I correcT?

Hi Eric,
Appreciate this is a really old post - but did you get round this?