No. The high isp is to match the IRL burn times of each stage [I think] and [probably] does not reflect true engine efficiency.
In this case the high isp is for normal mode and the 1.5 scale factor of realistic made the isp even higher.
The difference between him and me is that I make them in less time, there is less quality of course, but you still have a titanium mod while waiting for the brioche one.