From the article: "with two ports open the VTF-1 MK3 is rated at 103dB at 25Hz versus the 93.9dB of the older model at the same Hz measurement"
That is a huge improvement, more than three-fold increase in output. One thing that might have slightly contributed to that increase is that the ports are now on the same side of the cabinet as the driver, which would bring both a tad closer to the testing microphone, but that would only add a very slight amount to the measurement. I also like the response of two port mode hitting 110+ dB at 40 Hz and above, making it a great little sub for music.