Early versions, pre-torsion spring, Eagle Mike doohickeys did not have that groove. Eagle Mike supplied with two improved springs of different lengths and that appears to be what has been installed here. Since you have it you may as well install the new version and torsion spring. Current one looks to be doing its job.The lever currently in the bike is not an EM piece. Those have a groove around the top edge for the torsion spring to sit in. Install the kit you got if it has the torsion spring. I’m surprised the regular spring still is some tension in it.