To my eyes mighty mouse's ground approach looked like bjj, though I knew AMC wasn't a "Bjj " school. However, I really haven't seen a lot of catch style ground game except for some of the MMA guys like Sakuraba, Shamrocks, Barnett. Are the grappling styles close enough to look pretty similar?
IMO, grappling is grappling. There are only so many ways to twist, crank and choke the human body. There is a reason many different cultures used very similar wrestling/grappling moves without any cross pollination.
As far as his style it was very Catch influenced IMO, the aggressive takedowns, aggressive guard passing followed quickly by setting into a submission flow keyed off the DWL/Kimura grip. Giving up submission attempts to either stay on top or stand back up.
There was one instance toward the end of the third where he stepped over for the DWL/Kimura, stayed on top for awhile then feel back and as soon as he realized he didn't have it he right away used the hold to pull his hips out and get back up rather than hold the submission and stay on his back.
Just after this he gets taken down off a nice single leg switched to a far side knee tap and lands with Maraga in his guard with a guillotine/front headlock locked up, again instead of falling back for the sub attempt he uses the hold to pull his hips out and stand back up.
Also the standing guillotine/front choke in one of the earlier rounds instead of jumping guard to lock the choke up.
These are all staples of Frank Shamrocks grappling, Frank and Hume have similar grappling lineage.
Maybe KJ could shed some better light on this.