Interesting observations. I'm not sure how it actually works or why it would be different between platforms. When I used PP on android and only about half the channels populated, I edited the xml and deleted lines in the <channel> fields and changed the channel name if need be so that channel name matched what was in the m3u. My m3u doesn't use tvg-id at all, so in my case the IDs don't matter. I no longer use PP however, preferring to have everything within the media center app, in my case it's Kodi.
I'll see if I can find an explanation on the author's website so we have a definitive answer. Inquiring minds want to know.
I've asked over at niklabs to see if we can get an explanation on this.
EDIT: It does pull data from only the last line of the display-name.