If you wait to long your spot can get filled just as always. I don't think the portal changes it very much. If you are a top end recruit for a school they probably find a way to fit you in and not take a commitment from another position. I think its possible schools now also have the ability to fill spots with the portal instead of freshman, but I think schools probably lose as many to the portal as they get so that is likely a wash numbers wise. I think coaches probably let their legit offered players know where they stand regarding commitment timing and their position filling up.