Change from SH match to 3% SHNEC after match notice?

Employer handed out a 2021 safe harbor match notice early and now wants to change to a 3% SHNEC for 2021. Are they obligated to the 2021 SH Match because of the notice, or can we get a new notice out by tomorrow and change that?

Same exact scenario here.   We got them the 3% notice last week so you should be fine if they distribute it timely.

Thank you. New notice is going out now!