Hi,
I couldn't really find the statement you mentioned in the current version of the Developer Guide SPS 06.
However I can tell you that by definition of SQL those statements have a slightly different meaning and thereby produce different results depending on the data.
The t2.c2 = 'A' in the second statements' WHERE clause is interpreted in an 'INNER JOIN' way, thereby for all rows in the result set this statement has to evaluate to true, otherwise they will be filtered out including the left hand side table rows.
The LEFT JOIN predicate instead only makes sure, that left hand and right hand side rows are matched together which satisfy the predicate, but if there's not a single match for a single left hand side row, the left hand side row will be in the result set anyway. (with null values as default for the right hand side result columns). So in easy words it hard filters only the right hand side, but not the left.
Regards Christian