Some might have dismissed this information last December. Many likely haven't seen the label on the bottle, and in any event the constituents of each mRNA patented vaccine (apart from "delivery platform") aren't public knowledge. Which isn't to suggest expert organic chem knowledge is required to understand prerequisite novelty in design to acquire a patent.
btw,
Where's muh patent waivers?
WHO makes interim recommendations for mixing and matching COVID-19 vaccines
EU agencies endorse mix-and-match of COVID-19 vaccines

archived
Japan breaks ranks
LIVING OFF ebola marketing mix 'n' match UPDATE
How'd that work out?