Locust Swarm’s damage per locust consumed does not get converted/adapted when the skill is converted to cold by the Frost Bites node in Swarmblade Form.
Frost Bites specifically states that Locust Swarm, Swarm Strike, and locusts are all converted to cold. However, Swarm Strike is still applying +15 physical and +15 poison damage to Locust Swam per locust consumed (as stated in the tooltip Alt text), so it still deals primarily (~95%) physical and poison damage after being converted to cold damage.
I believe this was just missed during the change to “adaptive” melee damage and Swarm Strike’s effect and tooltip should instead be +30 melee damage to Locust Swarm per locust consumed so that the damage matches the skill tags and visual effects after conversion.