Illinois

current law includes this:
(A) The third offense was committed after July 3, 1980.

so while the whole law is dated as effective much later (2009) the original underlying statute must have been created on or prior to July 3, 1980. and actually the current revision (already scheduled to change come Jan 2018) was effective 2009 so yes Illinois did have a three strikes law at the filming time in question.

as for drifting language, faux pas' of minor nature likely occur daily with grievous error evident of geographic and/or cultural differences showing too often to catalogue despite the industry hiring continuity people and expert advisors. we shouldn't nitpick if the law says "Habitual Offenders" while every red blooded American says "Three Strike Law"

perhaps the writers misconstrue simply because back in the 1970's it hadn't been given the catchy baseball phrase or maybe because it isn't convenient to include a state that doesn't allow a petty theft to become a life sentence (Habitual criminal act applies only to the most dangerous and most heinous of crimes, no misdemeanors, not even those enhanced to a felony due to recidivism, can receive the dreaded life sentence enhancement.