please explain what the orange train is supposed to do in the station, when the yellow train hasn’t even finished loading?
if a train has to wait because another train on the same line and travelling the same direction is already occupying the station, then you either have too many trains on the line or your trains are not spread out yet and deliberately have to wait.
if trains would bunch up and then just choose another platform you might end up having three platforms blocked by three trains of the same line, all waiting for loading and your other two lines that need to go into the station can’t even use the station.
what you are trying to achieve is neither prototypical nor makes any sense, so don’t compare it to openttd. TF is not openttd, obviously some stuff will work differently and you have to get used to it. what is a roro-station supposed to be?
in this case there is no bug or lack of feature (the only thing lacking is waypoints, but they’re on their way), you’re simply doing it wrong.
and if you want different lines to use different platforms, then at this time until we get waypoints you have to seperate them by signals and track layout. that is a lack of feature indeed but will be changed very soon.