Is there any real evidence of "shadow profiles" or are people just speculating due to confirmation bias? If you give millions of mutual friend recommendations there's bound to be a few that hit.
I have on my phone Facebook app and Facebook Lite, on Lite I have a fake account that I intended to use to like other things (see beyond my bubble) short story -never used account.
I receive push notification from Lite app to connect to new friends. People suggested are from my real account friend list and between the 2 accounts we don't have mutual accounts. I've visited my parents and suggestion to be friend with them pop up.