And guess what, when the government orders new a hammer for a project, they probably are not going to do anything to advance the design of hammers
And they aren't going to spend 300 million dollars on it saying it's to maintain U.S. leadership in hammers.
It would be a waste of money if it was being built to just study supercomputers,
Shame the people making the law don't look at it the way you do
"will ensure the United States retains global leadership in supercomputing."
but that isn't the point, as in these things are intended to be used to further other research, and nothing you've said suggests it is unable to do so.
If the other research goals can justify the cost let them just don't go around saying its goal is to advance supercomputing.