"a high load?" I see this for some regional trains, such as one going between Frankfurt Flughafen and Koblenz.
Such prognoses are often worthless for regional trains because there is no seat reservation for them. Only for peak times are such statements reliable, because, of course, experience shows that a commuter train is always full in the morning or evening. If possible, be at the platform in FRA a few minutes before departure, and when the train comes to a stop, go immediately to the next door to have a good "starting position". And if you still can't find a seat right away, look around and see where one of your well-mannered fellow passengers thinks his backpack should sit on the seat next to him, and tell him that you would like to occupy that seat.