I don’t think there is any reason that steaming wouldn’t work in almost the same way - you may have to steam a little longer and toss the chard mid-steam since it should collapse on itself causing the leaves in the center to be insulated from the steam.
The only other consideration I can think of between steaming and boiling would be reducing bitter components - but I don’t find chard bitter so this would be for other greens. The boiling water can reduce the bitterness of something like a broccoli rabe by leaching some of those compounds into the water.
