Isn’t the main purpose of S2 to be able to scan from different “directions”? More a purpose of Google Maps when viewing the world as a spherical object compared to Sqlite3 just using a simple B-tree index on lat+lon?
The individual cells being sized and being able to easily to compute neighboring cells seems useful for the described algorithm. I haven't given it much thought on applicability here, but it sounded somewhat similar to a search pattern I once implemented within pgsql to locate items on a map that were within proximity of a given latlong.