Great cite matt, thanks for the research.  Unless I'm pulling the wrong version of the regs, what I'm seeing from 1.199A-3(b)(1)(iv) says this:

"However, losses or deductions that were disallowed, suspended, limited, or carried over from taxable years ending before January 1, 2018 (including under sections 465, 469, 704(d), and 1366(d)), are not taken into account in a later taxable year for purposes of computing QBI."

https://www.irs.gov/pub/irs-drop/td-reg-107892-18.pdf

Rick