Robocopy ложно отмечает файлы как более новые

Да

Статистические данные столбца не восстановлены, только индексируют статистику

--random data
CREATE TABLE dbo.foo (bar int PRIMARY KEY, humbug char(2000))
INSERT dbo.foo (bar, humbug) VALUES (1, 'aaa')
INSERT dbo.foo (bar, humbug) VALUES (2, 'bbb')
INSERT dbo.foo (bar, humbug) VALUES (3, 'ccc')
INSERT dbo.foo (bar, humbug) VALUES (4, 'aaa')
INSERT dbo.foo (bar, humbug) VALUES (5, 'bbb')
INSERT dbo.foo (bar, humbug) VALUES (6, 'ccc')
INSERT dbo.foo (bar, humbug) VALUES (7, 'ccc')
INSERT dbo.foo (bar, humbug) VALUES (8, 'ccc')
INSERT dbo.foo (bar, humbug) VALUES (9, 'ccc')
INSERT dbo.foo (bar, humbug) VALUES (10, 'cc')

INSERT dbo.foo SELECT bar+10, humbug FROM dbo.foo

--generate index stats + column stats
SELECT * FROM foo WHERE bar = 12
SELECT * FROM foo WHERE humbug = 'bbb'

--created date
SELECT
    OBJECT_SCHEMA_NAME([id]) + '.' + OBJECT_NAME([id]),
    NAME,
    STATS_DATE ([id], indid)
FROM
    dbo.sysindexes
WHERE
    OBJECT_NAME([id]) = 'foo'
ORDER BY
    STATS_DATE ([id], indid)  DESC

--Relax, have a coffee

--rebuild
ALTER INDEX ALL ON dbo.foo REBUILD WITH (FILLFACTOR = 90)

--check again
SELECT
    OBJECT_SCHEMA_NAME([id]) + '.' + OBJECT_NAME([id]),
    NAME,
    STATS_DATE ([id], indid)
FROM
    dbo.sysindexes
WHERE
    OBJECT_NAME([id]) = 'foo'
ORDER BY
    STATS_DATE ([id], indid)  DESC

--only index stats were updated