Looks like we've found another frequency in use by this group. More listening (and research) is needed but this is promising knowing that you heard similar traffic to the station that recorded the traffic on 4630 kHz USB and put it on YouTube.
Hopefully I'll have some free time in the coming evenings to park a receiver (and/or remote SDRs) on 4630 kHz and see if I can hear them too. Considering previous logs of 15151.5 kHz and other higher-frequency logs, along with the dozens of 11 meter band frequencies in question and the various 6-7 MHz band traffic centering around 6900 kHz, I have a feeling there's another frequency or two out there, possibly on other bands. That does confirm the theory regarding at least some of these operators having the capability to operate all over HF, vs. only operating on 43 meters and/or 11 meters.