(2) Certifications completed after December 31, 2020. For certifications of plan status completed after December 31, 2020, the determination of whether a plan is in critical status or critical and declining status for purposes of eligibility for special financial assistance must be made using the assumptions that the plan used in its most recently completed certification of plan status before January 1, 2021, unless such assumptions (excluding the plan's interest rate assumption) are unreasonable.