We had a fitting that bolted to a long slug that slid into the sail track groove and locked in place. It was identical to the gooseneck pivot, so the rotation of the boom and the vang fitting matched perfectly.
That looks like the fitting for a Boomkicker, which supports the boom like a rigid vang and is used in conjunction with a soft vang. The loads are mostly compressive (see photo for fitting).
For a soft vang, I don't think I trust that fitting. On my boat I have a robust plate held in place with 8 or 10 rivets. The vang can really load up, don't undersize this fitting.