I have seen the sentence structure verb + day of the week (which skips the usual "on" preposition splitting the phrase) appearing here and there, e.g., in CNN's article noted below:
The Omicron Covid-19 variant is now the most dominant strain in the US, accounting for over 73% of new coronavirus cases less than three weeks after the first was reported, according to estimates posted Monday by the US Centers for Disease Control and Prevention.
I would like to know why the word "Monday" is not preceded by the preposition "on". I have seen an answer to a similar question, however, none of the reasons stated in the reply applies to the case I outlined. Is such use of English considered to be grammatically correct?