Try a different question: should I need to create statistics just to see how much space a table uses?
EXEC sp_spaceused 'test';
That query shouldn't just fail, right? Yet it provides the correct row count of 1000 rows. You can look at the code of
sp_spaceused quite easily:
@reservedpages = SUM (reserved_page_count),
@usedpages = SUM (used_page_count),
@pages = SUM (
WHEN (index_id < 2) THEN (in_row_data_page_count + lob_used_page_count + row_overflow_used_page_count)
@rowCount = SUM (
WHEN (index_id < 2) THEN row_count
WHERE object_id = @id;
This doesn't mean that the estimate "comes from the sys.dm_db_partition_stats DMV". DMVs are created for end users to write application code against. The approximate row count of the table is stored in some internal structure which can be used to provide a cardinality estimate when there's no other option available for the query optimizer. If you need to know the details about this internal structure you could try using a debugger, but it's not like there's any guarantee that it wouldn't change between SQL Server versions.
It's worth mentioning that you should almost never have tables without statistics in production.