In the oil field B-pressure welders have a similar devices on they're welding skids, it little more than a flat plate with a yolk of some sort welded to the centre, supported by two rather large bearing or a collapsable/foldable stand, either bolted or welded to the skid, just so they can do a continuous roll weld without stopping.
But that bottle jack/bowling ball welding table would be a dream for a structural welder...but they don't matter anyway.