The collection is described as Ireland, Civil Registration Indexes, 1845-1958, but in fact this is extremely misleading, particularly with regard to records from Northern Ireland.
However - I say predominantly. There are in fact some records for the north included in the database after Partition, but even with the wiki update, there is no indication of the extent of this coverage for Northern Ireland on the site - it simply says "Northern Ireland, 1922–present. Physical description not provided at this time". Most Northern Irish birth entries found in the database have a FamilySearch microfilm number but no volume number or page number, as with pre-Partition events. The northern post-1922 marriage records do have these details, as do the deaths.
At least the records prior to Partition are complete for the whole island, aren't they? Um, no! But the wiki update does show the gaps in all Ireland coverage prior to 1922 - for births, there are omissions in 1867, 1869, 1880 and 1892-93; for marriages no gaps are noted, and for deaths there are a handful of missing entries for the third quarter of 1894.