Any soft top that mounts using your bow hardware and door surrounds would benefit from that top arch bar, as it tensions the fabric, and helps keep water from puddling. Although, some don't care for them.
When I test drove a semi ratty LJ at a dealer, it had that part. The Jeep itself had several other issues so I test drove the TJ that I now own. It didn't have that part. Even though the TJ's top looked and felt much newer, it flapped pretty loud well below freeway speeds. Since nothing else seemed to be a problem I talked down the price as low as I could get it then told them I needed that brace. I don't know why but for some reason they seemed to prefer that I take the one out of the LJ instead of them taking it out. No biggy, it's stopped that flapping ever since.