This is not the case. Rather, they will not achieve research grade if the community ID is different from their ID. Frequently, these users will change their IDs based on what the community suggests, so adding IDs is definitely helpful. You may also be interested in this feature request:
https://forum.inaturalist.org/t/search-by-observation-taxon-or-community-taxon/3620
This is also not true. Needs ID also counts.
(Not sure why there’s casual observations though.)