My ‘04 has Velcro straps there… to hold “something”…. I use it to hold a charging cable. Looked in Realoem.com and didn’t see anything in “trim” on the parts list.
I looked at info on part#5 (flap) …
https://www.realoem.com/bmw/enUS/sho...diagId=51_4939
It could be part of the various versions of #5