Just as 2 ids for Species level can achieve research grade, I gather 2 ids for Genus level can do the same if the net vote for improvement at that level is “can’t improve”.
Although Subgenus is presumably finer than Genus, it does not behave in the same way. For instance, if this example were at Genus level. I’d think it would have moved out of Casual and into RG by now, but that’s not happening yet despite full agreement of Subgenus: https://www.inaturalist.org/observations/317485