For what it's worth, I see no moral, ethical or legal obligation to "make whole" the HCEs whose 401(k) contributions were at a high enough level for the plan to fail ADP testing. It looks to me just like another effort to take care of the HCEs. Had there been more timely efforts to hold down the HCE contributions, the HCEs would have been on the hook for higher 2016 taxes instead of higher 2017 taxes. The entire regulatory structure is intended to keep HCEs from deriving too big a tax benefit from the 401(k) plan when the level of contributions from non-HCEs is on the low side. Why should there be any pressure on the sponsor to make anything up for the HCE's?