That's a direct heat electric system....not RIMS. Like the other poster said, all things being equal, you can get the same efficiency out of a BIAB system as a traditional brewing, even in a big brew.
I have a recirculating BIAB system, and the recirculation does bump the efficiency a bit. The electric really has nothing to do with efficiency.
One of the reasons you hear sometimes that it is difficult to get good efficiency out of BIAB batches is just because it is difficult to "squeeze" as much high gravity wort out of a 15+lb bag than it is a 10-12lb bag, so you tend to lose more wort to the grain in a big, heavy BIAB grist.
I do 5-5.5 gallon BIAB batches, recirculate, double mill my grain, and use direct heat propane. My last batch was a 13.5 lbs of grain Baltic Porter with a OG of 1.08, and I hit 78% efficiency and expect about 7.9% ABV.
Some people that do bigger batch BIAB will mash with partial volume , pull the bag, and actually do a sparge of 170F water through the bag to wash the grain and complete the volume prior to the boil. It's an extra step, but will help with that big batch efficiency by rinsing more wort from the grain.