Not using the noun, no. "Making stuff up" is untruthful behavior.
That was the trigger. The last I heard, suggesting that a person engages in making stuff up, that's the same as lying. Unless that person is writing fiction (and says so) or is delusional, and is making stuff up but believes it's true. We could say one of those two things about ER, but that would be making stuff up.
Tom, you have made remarks based on statistical evidence that could be interpreted another way. You didn't make stuff up any more than ER did. You just interpreted it in a way that not everyone agreed with. It's a shame you didn't extend that courtesy to him, which makes your use of the word "diplomatic" elsewhere in the thread pretty hilarious.
Just sayin'.