I have never dealt with this but it seems that form 1099 misc box 3 (other income) has the potential to be treated differently than box 7 (self employment income).
Yes, the earned/unearned dilemma when it comes to taxable scholarships and kiddie tax is confusing.
You can look form 8615 up on the internet.
I don’t know why the calculation is the way it is.
Did you do a preview of the tax return and see what forms are generated?