Is accurate info on parents taxes necessary if using TCJA rules?

If I elect to NOT use Pre-TCJA rules, as far as I understand unearned income would be taxed at the trusts and estates rate. This wouldn't depend on my parents income or anything of the sorts, but the 8615 form still asks for that information (parents taxable income, parents qualified dividends, and parents capital gains).

 

I don't have that information on hand and my parents might not have it for a decent while (and might file for an extension), and I'm wondering if it's actually necessary for me to enter completely accurate information in those fields, or if ballparks are good enough.