if trains are waiting for full load and you have more trains on the same line waiting to get to the station then you clearly have way too many trains on that line for the production capacity and they will just loose money. and it won’t speed up the proceedings if trains would choose a different platform because then you would just have more trains waiting in the station for full load, clogging up the station for other lines.
with the waypoints which will be introduced soon you could just as well organize your lines in such a way that trains would wait in seperate tracks in front of the actual station without obstructing the through tracks (real freight yards have more than just one group of parallel tracks as well).