If I give my kids $5 and tell them to use it for getting a snack, I can't call it fraud, waste, and abuse if they choose a Snickers from the vending machine instead of a granola bar just because I think they should have chosen a healthier snack. If they pocket the $5 and then go ask their mom for a snack then that's fraud. If they use the $5 to buy a mini Snickers from the kid in the bus, that's waste. If they buy a bunch of soda that's abuse.
In this instance, I have a kid who isn't spending the $5 I gave him because he doesn't like what his sibling got with their money yesterday. Either way, I already allocated the $5 to snacks and I don't get it back, so If I want to change things I either give them more direction on how the money should be spent or give them less than $5.
The executive branch has the power to change how that slush fund gets spent moving forward, so long as it abides by the same rules and regulations. I hope they don't award another dime to a cause that doesn't directly advance our agenda. They don't have the power to change previous awards and they don't have the power to just not spend it. Reference
https://www.gao.gov/products/095406, which I'm sure will have a bunch of legal challenges to it.