SQL 2012 :: CheckSum Agg Function Returns 0 For Even Number Of Repeated Values?

From what I've seen, the CheckSum_Agg function appears to returns 0 for even number of repeated values. If so, then what is the practical use of this function for implementing an aggregate checksum across a set of values?

For example, the following work as expected; it returns a non-zero checksum across (1) value or across (2) unequal values.

declare @t table ( ID int );
insert into @t ( ID ) values (-7077);
select checksum_agg( ID ) from @t;
-----------
-7077
declare @t table ( ID int );
insert into @t ( ID ) values (-7077), (-8112);
select checksum_agg( ID ) from @t;
-----------
1035

However, the function appears to returns 0 for an even number of repeated values.

declare @t table ( ID int );
insert into @t ( ID ) values (-7077), (-7077);
select checksum_agg( ID ) from @t;
-----------
0

It's not specific to -7077, for example:

declare @t table ( ID int );
insert into @t ( ID ) values (-997777), (-997777);
select checksum_agg( ID ) from @t;
-----------
0

What's curious is that (3) repeated equal values will return a checksum > 0.

declare @t table ( ID int );
insert into @t ( ID ) values (-997777), (-997777), (-997777);
select checksum_agg( ID ) from @t;
-----------
-997777

But a set of (4) repeated equal values will return 0 again.

declare @t table ( ID int );
insert into @t ( ID ) values (-997777), (-997777), (-997777), (-997777);
select checksum_agg( ID ) from @t;
-----------
0

Finally, a set of (2) uneuqal values repeated twice will return 0 again.

declare @t table ( ID int );
insert into @t ( ID ) values (-997777), (8112), (-997777), (8112);
select checksum_agg( ID ) from @t;
-----------
0