Last year, when our Facebook canvas app sent an app request using the FB.ui request dialog API, the request showed up in 3 places for the recipient(s):
It appears that Facebook has removed the notification when you send someone an app request. I've tested this on two different apps and sending an app request does not result in a notification being sent to the recipient.
Two questions:
This definitely WAS a bug per: https://developers.facebook.com/bugs/532388000129311
It appears to be resolved now. A pretty heinous breakage on the part of the Facebook platform, if you ask me.