Good luck in Indiana! I'm in MN, which has a ML season following the firearms season by about two weeks, plenty cold and sometimes with no snow, sometimes with 24".
Legal ML can be 40 cal rifled, or 45 cal smoothbore or larger, but cannot have optical sights. That leaves you OK with all the day-glo stuff, with plastic stocked in-lines, sabots, SS fluted barrels, etc. To its credit, the MN DNR has never called this a "traditional' season. FWIW, one can use any ML (including a pistol) with any sights in the shotgun-only zones. Never did figure that one out!
I suspect money plays a big part: big box stores sell in-lines for less than what one would would pay for a traditional sidelock, even a Lyman or Thompson. The DNR wants the revenue from the license fee, the hunters like the extended season.
The no "optical sights" was a compromise regulation from those that wanted traditional side-lock only, and the 'scoped in-line folks, so in-lines OK, but only iron sights.