No, you are not over-reacting. One of the checks to make sure the leads are in the proper location is that your toes may flex. See the following:
http://www.medscape.com/viewarticle/570942_7
https://www.icsoffice.org/publications/2005/pdf/0260.pdf
http://www.seekwellness.com/incontinence/interstim.htm
~Pete