Yes, the DOE does research on various energy related topics to prepare for the future. First you suggest they should be investing in supply side research (thorium reactors), then you say they shouldn't invest in demand side research (desalination)?
If you look at, y'know, energy use in the US [1] then desalination doesn't even rate a mention as an energy sink. The biggest source of waste by far is the 66% losses during energy generation and in electricity and transport. Realistically they should be focusing on the supply of energy.
And to be fair they probably are. I'm repeating myself, but this looks like the bureaucratic equivalent of someone with a bee in the bonnet and nobody could be bothered to tell them no.