If the child starts college in 2018 then whatever was contributed by non custodial parent 529 in that year 2018 would show up as ‘money paid on student’s behalf’ on the 2020/21 FAFSA (junior year).
So if that money is not contributed until 2020, it won’t show up on his FAFSA, if he graduates in May of 2022.
(good tip above).
Also it would show up as an item in the INCOME column of the student. Not as an asset. So it might not have an impact on FAFSA EFC at all.