Is Divine Mercy Sunday optional?

[Father Chris Alar](https://marian.org/marians/meet/chris-alar) a Marian father who does a great job of promoting Divine Mercy devotion mentioned on the [US Grace Force podcast](https://open.spotify.com/episode/5WwNwbQkmF3ozcBGO4EKMe?si=7e54346347fa4c19) that the Missals saying "2nd Sunday of Easter or Divine Mercy Sunday" was a mistranslation, that there's not an option and that everyone is supposed to celebrate Divine Mercy Sunday. That the "or" that we've seen in recent missals should be translated "namely". Are there any other instances of feast days (especially Feasts celebrating God) that are optional? Do they use the same wording, are there any other feasts that use the word "or" which are not optional?