Sort Warnings are generated when explicit sorting of queries is spilled into tempdb when there are less memory buffers left. Index maintenace scripts do NOT generate these and the expectation is, these shouldn't happen for Update Statistics also. Here is a code snippet generated from Update Statistics.
SELECT StatMan([SC0], [SB0000]) FROM
(SELECT TOP 100 PERCENT [SC0], step_direction([SC0]) over (order by NULL) AS [SB0000] FROM
(SELECT [cEndDateTime] AS [SC0] FROM [dbo].[Tablename]
WITH (READUNCOMMITTED,SAMPLE 5.949706e+001 PERCENT) ) AS _MS_UPDSTATS_TBL_HELPER ORDER BY [SC0], [SB0000] )
AS _MS_UPDSTATS_TBL OPTION (MAXDOP 1)
In the above query, note the Order by is used inside a sub query with top 100 percent. Queries like these generated from Update statistics are leading to hundreds of sort warnings on my server which could have been avoided. Can you provide some documentation on why you need to use TOP 100 percent with order by inside a sub query for Update Statistics or better yet do NOT fire these warnings for Update Statistics.