I did some test and yes, you are right. It's happen only with Apple devices. On the iPad it's fully shown directly on the CNA but you can't download it. On the iPhone it's the same but you can't fully see it also.
Using an Android device, even from the CNA, file, after clicking on download PDF, is automatically downloaded in the download folder of the device.
I've just advised developers about this. They told me that they are going to check and then they will do something to make the PDF downloadable from Apple CNA too.