Infantry formations that marched 50+ kilometres a day won't be as combat effective as those that didn't, but attrition from movement isn't modelled as the game system uses an "all inclusive" OP system now. That's not a problem per se, in this case infantry OP's are higher to allow them to move into enemy territory, but that also means German infantry units can move ~20 hexes over friendly terrain (and that was cross country, if you select one of the infantry divisions the Germans start with on turn one, it can travel 20 hexes to the North). After 80 kilometres of cross country walking in July heat, your feet won't be a pretty sight. You can probably forget about trying that the day after. Also: the German summer uniform was pretty heavy and not all that comfortable, a Rifle Regiment would be travelling lighter and be more used to hardship than a typical German infantry formation.
As such, movement rates are slightly unrealistic over friendly terrain, especially as they can do it every day. In the DB series, you could have your guys march 50+ kilometres each day but they'd burn through OP reserves quickly through extended movement.