Why does sys.fn_xe_file_target_read_file require an explicit cast on datetime2 column?

According to the documentation the returned column timestamp_utc should be of type *datetime2(7)* But when I query like this

SELECT 
    *
FROM sys.fn_xe_file_target_read_file('system_health*.xel', null, null, null)
WHERE timestamp_utc > dateadd(hour, -1, GETUTCDATE())

It returns no rows. It returns the rows only when I add an explicit cast to *datetime2*

SELECT 
    *
FROM sys.fn_xe_file_target_read_file('system_health*.xel', null, null, null)
WHERE cast(timestamp_utc as datetime2(7)) > dateadd(hour, -1, GETUTCDATE())

Which matches the last example in the documentation (even though no attention is drawn to it) Why is that?