It is 100% required for employment-based green card from a H1B. Anyone that has gone through this process knows this as their own job had to be posted to several job posting sites and each and ever candidate had to be reviewed and discounted in some ways (my company added crap to the posting such that it was simply impossible for someone to be as qualified for the job as me unless they sat next to me and did what I did for 5+ years…)