RMDs for survivng spouses

The SECURE Act changed the RMD for surviving spouses to the date the participant would have attained age 72. (401(a)(9)(C)(I).

What is the effective date?  The Act says that the effective date for the age 72 change is participants who attain age 70 1/2 on or after 1/1/20.  (The effective date for the stretch rules is participants who die on or after 1/1/20).  So what about participants who died before 2020 and who would not have reached 70 1/2 by 1/1/20?

Assume a participant who died during 2019 at age 68.  Does his spouse get to wait until he would have attained age 72, or because he died before 1/1/20, does she have to take when he would have attained age 70 1/2? 

I haven't checked in a few months but I thought participants who died on or before 12/31/2019 are subject to pre-Secure Act rules and that participants who die after 12/31/2019 are subject to Secure Act rules.