Thanks for reaching out. I am assuming you are trying to scroll document pages while the Place window is open. This is an expected behaviour on all Adobe applications. When the any pop up windows like Save/ Place/ Export is open, you can not scroll the document in background.
I will pass on your feedback to our Prooduct team and you could do that too by posting it here (https://indesign.uservoice.com/).
This is the best way of communicating with the Engineering and Product Management teams regarding issues and suggestions so they can be implemented in future releases.
"This is an expected behaviour on all Adobe applications. When the any pop up windows like Save/ Place/ Export is open, you can not scroll the document in background … "
That seems correct now, but not in previous releases.
I've checked in Adobe CS6 and you can scroll the document behind the Place pop-up menu (I knew you could). In Adobe CC this function no longer works – which slows the design and layout process down.
It's a real shame it no longer works as it was very usful – especially producing books with many images in.
I understand your frustration, Nathan. I have passed on this feedback to our Product team and would request if you could also post it on our UserVoice page and share the link here, so that we have a significant number of votes for this feature request.