I have an upcoming travel ZWS -> FRA -> OPO, and I just realized the "flight" from ZWS -> FRA is through Lufthansa Express Rail from the Stuttgart Hauptbahnhof and the layover in FRA is just 1 hour and 15 minutes. The problem is, how does the checked luggage work with this type of flight? I think I have to check it in at Frankfurt, correct?

Lufthansa's website says that for the Frankfurt airport the deadline for the drop-off of checked luggage is 60 minutes before departure, however, if I select "airport" Stuttgart Hauptbahnhof it says the deadline is 15 minutes before departure at "AiRail-Terminal in Frankfurt". So, which one is true? Because the layover is only 1 hour and 15 minutes, if the train is delayed I will likely miss the 60-minute window for check-in but if it is the 15-minute window I can easily make it. There is another "flight" from ZWS to FRA 40 minutes prior to mine, but I doubt they would let me board it without paying more.

Sorry if this has been answered before, but after intensively searching other websites I could not find an answer to this. Lufthansa's website for Express Rail is also quite useless in this regard.

Bonus question: On the way back, where do I pick up my checked luggage? Do I just leave the airport and head to the train station AiRail terminal to grab my luggage?