Basement "Edge" insulation
You really don't need it for insulation since it really does nothing,
Your slab is sitting on the soil and the footing. The footing is sitting on the soil also. The soil in that area is the same temperature as the soil outside the wall. All at that depth are about the same temperature because the of the relatively high heat transfer through all of the materials in all directions. It is not like warm air rising since soil conducts heat equally in all directions at the same rate.
Depending where you are, it will be 55-60 degrees just about all year long. The surface may vary slightly because of the interior air flow.
They probably put the foam in the joint to prevent it from getting clogged up and being ineffective some time down the road when it might be needed.