It's disinformation in the sense that what her grandfather did is irrelevant. It's not factual because it doesn't tell the whole story.

While it's true there were many Ukrainians who happily joined the Nazis and agreed with their anti-Semitic ways, it is also true that many Ukrainians were primarily interested in resisting the Soviet Red Army and hoped to reassert Ukrainian nationhood.

After the war, the Soviet Union painted all Ukrainians who resisted the Red Army as Nazis which is not entirely accurate. It's an old trick from the Soviet playbook which Putin is very familiar with. It's also known Putin has it in for Freeland. Personally, I think it's because she understands him too well for his own liking. She wrote "Plutocrats: The Rise of the New Global Super-rich" which is implicitly critical of the plutocracy Putin is busily setting up with his cronies.

Either way, perhaps she should have come cleaner sooner, but it really is a misleading story to begin with.