First, you went from a prolonged severe drought to a very intense rainfall in a very short amount of time, extremely not helped by the massive surface runoff when the emergency spillway was put in use. I don't know all of the geological processes involved, but the upper soil layers were probably made far more mobile and less stable by the drought.
Second, the massive erosion is happening on a slope, whereas the Grand Canyon is (comparatively) flat. A steeper gradient means less force is needed to set sediment in motion.
If you want impressive floods, the Bonneville and Missoula floods are the largest known floods in history. Imagine floods with hundreds or thousands of times the flow rate of Niagara Falls, which cumulatively scoured the Columbia river region by hundreds of feet.
There are examples where rivers are much older than the mountains they pass through - like the Susquehanna:
So I follow the Little Colorado expecting an easy drift into camp but instead I have a gale force headwind and serious bits of uphill. So I didn't get there and I had to sleep in the tent held up by rocks with no let up in the wind, with an electrical storm to follow, one where I was the highest metal object around...
Next morning I woke up rough and set off on my bike, literally 1/2 mile away up the road were a group of cycle tourists from Yugoslavia and they pitched up in one of the roadside stalls. Had I not given in so easily the previous night I would have had a fun time meeting up with them and drinking properly... I was also oblivious to the time zone change so the next day came with a 'free' hour too.
I did go down to the very bottom of the Canyon and up the other side to continue my cycle tour of the wonderful U.S.A. These crazy dams (every river is dammed) were a huge part of my time there, riding across them and camping by them.
"U.S. Geological Survey hydrologist Jim O'Connor and Spanish Center of Environmental Studies scientist Gerard Benito have found evidence of at least twenty-five massive floods, the largest discharging ≈10 cubic kilometers per hour (2.7 million m³/s, 13 times the Amazon River). Alternate estimates for the peak flow rate of the largest flood include 17 cubic kilometers per hour and range up to 60 cubic kilometers per hour."
Fascinating geology and scarily impressive traces. Makes me wonder what will happen on Greenland or Antarctica.
The symbolic and scientific significance are large. This is an exceedingly large ice mass, it may persist for years, possibly decades, in the Southern Ocean. It may pose a threat to shipping (though there's comparatively little through the region), and may have impacts on local biology and ecosystems (habitat loss, habitat gain, habitat change).
The mechanisms of loss, calving, migration, persistence, and of resulting changes to land-based glacial flow, will be fascinating.
But in terms of portending a drastic increase of ice flows local to it, the calving has little impact, as compared to, say, a shelf loss proximate to the primary Antarctic land mass -- the Ross or Weddel shelves, for example, which have behind them a thousand kilometers and more of kilometer-thick ice. That will be an interesting occurrence.
Or the formation and destruction, say, of ice dams, on the Antarctic continent or Greenland, creating meltwater pools, perhaps hundreds of kilometers in extent, and suddenly releasing those, as the dams erode, into the oceans. Similar mechanisms created a badlands landscape in eastern Washington State as the prehistoric Lake Missoula formed and drained, perhaps dozens of times, releasing cubic kilometers of water in massive scours. A similar mechanism, probably in Canada, triggered a catastrophic sea-level rise, measured as I recall in meters, over the course of days to a month.
That would also make for an interesting news cycle.
Contextualisation of these types of events in the press is exceedingly poor, with a small handsful of exceptions. I've already mentioned Brad Plumer's Vox coverage in this thread, he's among the exceptions.