I've never heard of those "new security measures" and it wouldn't even make sense for Amtrak to try and enforce such a restriction. The trains aren't designed in such a way as to make that possible.

For example on a Superliner sleeping car, the luggage rack is downstairs, no where near a passengers in one of the roomettes. And there is no way to put the luggage into a roomette. One can barely fit two people in the roomette, along with a small carryon bag.

The only real restrictions are the weight limits, 2 bags per person, and the fact that all bags must be clearly marked with a tag indicating who the bag belongs to.