Again, this data represents
Again, this data represents NORMAL owners, not those who do modifications to maximize their range potential or hypermile every minute they're driving the car. Which is the point, since 99% of drivers, even in ICE vehicles, only rarely do those things as well.
Further, most drivers aren't going to sit in a freezing car with just seat warmers and their mittens. Sorry, but that's not how 99% of drivers in cold weather are. Remember: these are REAL WORLD, not hypothetical "if you do all of this, then.." It's also very likely that a large number of the LEAFs in this data set don't have seat warmers as they weren't standard until this year.
Also, the engine coming on does supply power to both the battery and the heat exchange for the batteries in the Volt, which is why they did not include the data.