Train crew (conductors) always have the right to walk through the car. If your train goes into Tampa Florida for example, the train has to reverse out of the station to a wye so it can turn around. If you are the end car, the conductor will be there watching for problems, manning the emergency brake, and communicating with the engineer on their radio.

https://en.wikipedia.org/wiki/Wye_(rail)

The new trainsets that Amtrak just ordered from Siemens Mobility come with cab cars, so the crew can use that to control the train and not be out in the weather (and have full gauges, etc.) The cab cars are part economy seating so if your private car is on that train, you will probably end up sandwiched between the cab car and the rest of the train and have people walking through.