Error in exclusion constraint error message (8.5)?

Hi,
I tried to use exclusion for time ranges, with this table and data:

CREATE TABLE test (
from_ts TIMESTAMPTZ,
to_ts TIMESTAMPTZ,
CHECK ( from_ts < to_ts ),
CONSTRAINT overlapping_times EXCLUDE USING GIST (
box(
point( extract(epoch FROM from_ts at time zone 'UTC'), extract(epoch FROM from_ts at time zone 'UTC') ),
point( extract(epoch FROM to_ts at time zone 'UTC') , extract(epoch FROM to_ts at time zone 'UTC') )
) WITH &&
)
);
INSERT INTO test ( from_ts, to_ts ) VALUES ( '2009-01-01 01:23:45 EST', '2009-01-10 23:45:12 EST' );
INSERT INTO test ( from_ts, to_ts ) VALUES ( '2009-02-01 01:23:45 EST', '2009-02-10 23:45:12 EST' );
INSERT INTO test ( from_ts, to_ts ) VALUES ( '2009-01-08 00:00:00 EST', '2009-01-15 23:59:59 EST' );

3rd insert fails (correctly), but I have doubts about its error message, which was:

psql:z.sql:18: ERROR: conflicting key value violates exclusion constraint "overlapping_times"
DETAIL: Key (box(point(date_part('epoch'::text, timezone('UTC'::text, from_ts)), date_part('epoch'::text, timezone('UTC'::text, from_ts))), point(date_part('epoch'::text, timezone('UTC'::text, to_ts)), date_part('epoch'::text, timezone('UTC'::text, to_ts)))))=((1232078399,1232078399),(1231387200,1231387200)) conflicts with existing key (box(point(date_part('epoch'::text, timezone('UTC'::text, from_ts)), date_part('epoch'::text, timezone('UTC'::text, from_ts))), point(date_part('epoch'::text, timezone('UTC'::text, to_ts)), date_part('epoch'::text, timezone('UTC'::text, to_ts)))))=((1232078399,1232078399),(1231387200,1231387200)).

Please not that both box values are the same, and relate to row:
( '2009-01-08 00:00:00 EST', '2009-01-15 23:59:59 EST' )
while I would assume that one of the boxes in error message should relate to row:
( '2009-01-01 01:23:45 EST', '2009-01-10 23:45:12 EST' )
I.e. contain box: (1231645512,1231645512),(1230787425,1230787425)

Is it my lack of understanding? If yes, what is the rationale behind providing the same value twice?

Best regards,

depesz

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