My '17 and its' replacement, the 2019 Transit cargo, had this irritating thing on the seat belt. It's a vinyl cover of some sort, where the belt anchors to the (power) seat. I have no idea what it's purpose in life is, other than to rub across my butt every time I get in or out of the van.
Fed up with this, yesterday I finally fixed the problem forever. I cut the stupid thing off.
First, remove the staple holding it to the seat belt. Then pull it up.
Then cut it off! It's pretty thick, so I used wire cutters.