Earlier quoted context omitted.
I experience the same thing and it's really frustrating. I refuse to install Facebook applications on my phone, and they've needlessly crippled their mobile site (disabling messages except mbasic.facebook.com among many other things). If I so much as check a notification then go back to the newsfeed, it's different content and hit/miss as to whether I can find the top post again.
after them crippling their mobile site I deleted facebook, it was not needed... though I just replaced it with whatsapp or hangouts (really hard to get my friends on anything else)
Years ago I had the app installed. The fact that they wanted not one, but two hugely bloated apps on my phone is the reason they haven't been on my phone in many years.