What am I not understanding about DateTime::SpanSet::intersects()?

In the code below, why do the span sets not intersect when the spans taken from them do?

I've tried this code on both Red Hat 5.2 and on Mac OS X 10.5.

DateTime: 0.4501
DateTime::SpanSet: 0.25
DateTime::Event::Recurrence: 0.16

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next start 1: 2008-12-17T07:00:00
next end 1:   2008-12-18T07:00:00
next start 2: 2008-12-17T17:00:00
next end 2:   2008-12-18T17:00:00
spans intersect: yes
span sets intersect: no

=======

use DateTime;
use DateTime::SpanSet;
use DateTime::Event::Recurrence;

my $start_1 = DateTime::Event::Recurrence->weekly(days => 3, hours => 7);
my $end_1 = DateTime::Event::Recurrence->weekly(days => 4, hours => 7);
my $span_set_1 = DateTime::SpanSet->from_sets(start_set => $start_1, end_set => $end_1);

my $start_2 = DateTime::Event::Recurrence->weekly(days => 3, hours => 17);
my $end_2 = DateTime::Event::Recurrence->weekly(days => 4, hours => 17);
my $span_set_2 = DateTime::SpanSet->from_sets(start_set => $start_2, end_set => $end_2);

my $now = DateTime->now();

my $span_1 = $span_set_1->next($now);
my $span_2 = $span_set_2->next($now);

say 'next start 1: ', $span_1->start();
say 'next end 1:   ', $span_1->end();
say 'next start 2: ', $span_2->start();
say 'next end 2:   ', $span_2->end();

say 'spans intersect: ', $span_1->intersects($span_2) ? 'yes' : 'no';
say 'span sets intersect: ', $span_set_1->intersects($span_set_2) ? 'yes' : 'no';