Don't shut down WhatsApp on your iPhone by swiping up

Of late, the message that WhatsApp users are getting urges them not to do this

It's highly bizarre and grossly baffling.
If you are using WhatsApp on an iPhone running iOS 11, you might have received a message which asks you not to shut the app down by swiping up. That's strange - since there's no other way to close it.  
Except the iPhone X, on every Apple mobile one closes down apps by double-clicking the Home Button and then swiping up to close the windows one doesn't want to keep open using the "app switcher".
As far as iPhone X is concerned, you need to swipe halfway up the screen, hold for a second on an app and then swipe to shut it down.
Of late, the message that WhatsApp users are getting urges them not to do this.
"Swiping to close WhatsApp can prevent you from receiving notifications," the message says. This may possibly mean you could miss WhatsApp message notifications.
Here's the video of the notification, which was sent to a Twitter account operated by Apple's tech support team.

Like this. Open the Multitasking screen, swiping up on the WhatsApp app to close it; as seen in the video. pic.twitter.com/yeOErcAbIz
- grehivin (@grehivinvz) November 1, 2017

It's been suggested that the problem started when Apple launched iOS 11, the new operating system for iPhone and iPad which introduced a change to the way users view notifications - which are the messages which pop up whenever messages or alerts are received, a report in The Sun reported.
The website WABetaInfo, which specialises in covering WhatsApp, claimed on Twitter: "WhatsApp is testing a workaround to fix push notifications.
"This is an iOS 11 bug."