No because "smart" genes don't sustain. Like 50% is volatile noise. So that would actually line up. I.e. Two 150 IQ don't have a 150 IQ on avg. They have a 125 IQ, and then the two 125 IQ have a 112, and the two 112 IQ have a 106 and voila.
That said, the grandparent's figure are rather wrong, for two reasons. First is that the heritability of IQ is typically estimated to be around 0.8 instead of 0.5, which means that the expected IQ of parents with IQ of 150 is 140, instead of 125. Second is that this is only the expected IQ. If they have multiple children, some will typically be above the expectation, and some below. More specifically, given standard deviation of 15, around a quarter of children of parents of 150 IQ will have IQ of 150 or higher.
This research is not new, it has been done for many decades now. The word “heritability” has a well established technical meaning.