Total excursion would be the area under the graph, if you start at the tuning frequency and go up to say ~200 Hz you'll get the total excursion of the driver at those frequencies. Or you can restrict the signal in to the frequencies of interest, but the graphs Rob posted are misleading because they are zoomed way out and signal is shown down to 5 Hz when the tuning frequency looks to be just under 30 Hz. If you zoomed in on the the 25-100 Hz range you get a much clearer picture, but Rob didn't do that...
In any case, it's obvious from the graphs that excursion of the BR woofer is MUCH lower around the port tuning frequency and the resulting FR graph shows a large increase in bass extension and efficiency, which is exactly what you'd expect.
IMO Rob's argument is completely a semantic interpretation of the data and serves no useful purpose. Anyone can look at the graphs he posted, it supports everything I said, which btw does NOT include saying it's definitely going to cause any damage to plug a port! The tradeoff is lower efficiency and increased IMD due to higher excursion.