They are the same design so they are interchangeable but they are NOT the same. The part numbers, drop and I would imagine the spring rates are different as well. The sportlines for an EK are a 1.8 drop while the EK Si is a 1.6 drop. The G3 Teg suspension is a 1.7" drop
But look on the bright side, if they made springs for 2 different cars the same, it would be pretty stupid, like you stated. So you were right on the logic.
