Hello,
It appears that some summoning themes (Spiders for example) receive the (summoning point) discount that SF/GSF: Conjuration provides when summoned via the custom spell, "Summon Swarm"
However, other themes (Insects, for example) do not receive any discount.
I do not know from one theme to the next which one incorporates the discount and which one does not.
I can verify though that insects (1) costs 10 per summon when conjured via the spell "Summon Creature 1" while costing 25 *each* when conjured via the spell "Summon Swarm" (For a total of 75 points instead of 30).