I dont know why, a lot of companies do a lot of the crazy pricing they do. I have seen some ludicrous pricing over the years on products that were identical other than the wrapper. I worked at the company and know first hand the packaging was the only difference. As long as people think they are getting something better they kept selling them that way.
As far as the 2 rods I don't have them to hold so that part I cant compare. That is why manufacturers should be listing the features that will help sell the products and show where one is worthy of the higher price point.
As for if they are using the same SCIII blank unless the people making these rods have royally screwed up it states on their website right here on their BLANK MATERIALS GUIDE page SCIII - Featured in Avid Series®, Avid X, Avid Pearl, Mojo Bass, Avid Series® Inshore, Avid Series® Surf rods.
Maybe they are considering the 10 more years of warranty on the AvidX along with this listed different from the Mojo Bass in the Features to justify the price?
I dont know about a catch but I agree the reviews of the new Mojo rods are pretty good across the board from what I have read.