Does birchat hachodesh need three (or four) people preferably as a commemoration to Beth Din?
Thanks to @Moshe for the reference which says in part
Mishnah Berurah then notes that blessing the month is not similar to the sanctification of the new month that would be done during the time of Sanhedrin. Rather, the reason we bless the new month is so that people should know which day is Rosh Chodesh so that they will be prepared to observe its halachos
which makes it clear that the ceremony is not a commemoration of the sanctification of the new month and so does not need 3 or 4 people.