So that I'm not misunderstanding, this is going to allow brand owners to manage the data that comes up on the right-hand panel during a Google search?

I don't think that's too bad. Especially if Google hasn't crawled the data correctly or references outdated information. I imagine Google will limit any "advertising" (i.e companies giving marketing bio's instead of factual bio's from Wikipedia) that might take place there if they're not monetising it. Although it does open the option for them to do it in the future, which is a worry.