Oh, now I realized you said >>>first<<<< rinse. I was confusing it with last rinse.
That's a cool down phase for three main reasons.
1) Kill suds: some "intelligent" detergents and oxy bleach react with a temperature change and the foam simply dissapears. It helps rinsing. every single bubble killed before the rinse is significant in a HE machine.
2) Reduce load temperature gradually: It avoids wrinkles.
3) Safety: If the machine is draining in a laundry tub, one could me burned by the hot water suddenly comming out of the drain hose. There should be a standard saying that, otherwise the manufacturers wouldn't make their machines spend a few more drops of water only for the reasons 1 and 2 as those drops count on the efficiency label.
The cool down fill won't spend significant water and can reduce the temperature up to 10 degrees C. It can reduce even more if the tap cold water is colder.
My Affinity does that too always the temperature is above 53C and trips the safety lock (the door won't open even if you unplug the machine) at 56C. I think maybe all FLs do that.
Some older euro front loaders turn off the heating element on the last minutes of the wash or add some cold water or do the both. These routines are efficient to prevent skinburns.