But if we have less than 100 in 2019, then we DON'T report in 2020 (because both of the prior 2 years (2018 & 2019) did not exceed the 100, correct?
Correct. Nor would you report in 2021. You have to be over the limit for 2 years. Thus, one year below the 25 or 100 threshold, takes you out of reporting for 2 years (for that type - loans or lines, or both).