Behaviour explained on iOS device for si.device.keepDisplayAlive property

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The si.device.keepDisplayAlive property is intended to keep the device screen on while performing long download operations.                    
It was introduced in Anywhere 7.6.1 version as we can see in "What's  New" document:                                                          
                                                                        
"si.device.keepDisplayAlive=true -  Use this property to specify if the display should be awake when performing long download tasks to prevent the app from locking and going to the background."                                                                                          
https://www.ibm.com/support/knowledgecenter/en/SSPJLC_7.6.1/com.ibm.si.mpl.doc_7.6.1/overview/c_new_features.html

So does it cover the following problem scenario?
 
iOS - lookup data download always interrupted when phone goes to sleep In Anywhere 7.6.2 (IFix from August 2017). The WorkExecution application on iPhone lookup data download gets interrupted every time phone goes into sleep mode (send app to the background and press power button to turn the screen off).

The next time user switches back to the app he/she receives an unexpected dialog: "Lookup data could not be downloaded. If you are connected, go to Settings > Refresh Lookup Data.".
 
Should the property si.device.keepDisplayAlive=true  prevent this from happening?

The short answer is no and long answer is that sending the app to background and turning off device screen will also stop the app from working. In this case the property won't interfere in the scenario.
So this behaviour is working as designed.

We do not support operations working in the background since we don't control how OS preserve it's  resources (battery, memory, etc).