This can be extremely dangerous. Only one appointment is guaranteed from the Senator's slate of 10. All others go into the national pool. If they are competitive in this pool, great. If not, no appointment. Period. Done. End of trip. What if one of these candidates had been the principal candidate on his local Representative's slate? He would have received an appointment. If is very common for the two Senators to coordinate lists. Nothing wrong with this. However, when local Representatives start leaving candidates off their list because they are on an unranked Senator's slate, especially without an LOA, very bad things can happen. If this is happening to someone, they should probably inform the CGO.
Conversely, if a Senator chooses to omit someone from his list who has a nomination from his local Representative, it is not good but less really bad things can happen. Should this happen across the entire state, those on the Senator's slate would be of an overall lesser quality than any of the 10 on each of the Representative's slates and the selection would probably not be the best candidate available.