I'm guessing the 777 and the 787 have a similar system, as we are all now rated on both
On the 787 below 225kts and with a high angle of attack you will get Autogap, ie: slats will fully extend.
So the Vref 30+40 will keep you below 225kts, and allow the Autogap function to work.
Why move the flap selector back to 1?
In the section about UNCOMMANDED FLAP OR SLAT MOTION -it states the conditions that have occurred to get the EICAS messages "Flaps Primary Fail" then "Flaps Drive".
Move away from commanded position
Continue to move once reaching command position
Move in opposite direction to commanded
So leaving the lever in 5 may allow the flaps to move, (highly unlikely as it also says the system will go to secondary mode and shutdown if there is any further movement)
but if the lever is in 1, there is no danger of movement as you haven't asked anything of the flap system.
Just my take on it