The tech is neat but the reasons this isn't already in use has to do a lot more with railroading company culture (operational familiarity, risk of losing business to a competitor) than with any particular shortcomings of the technology.

Right now, no one has to chaperone individual railcars (or bogies!), because trains of many railcars travel as a unit. This also makes track control / impact avoidance easier, regardless of the level of train control deployed on the track.

This may see more use in the EU, where EU-wide regulations are mandating all member states to separate ownership of their rail network from ownership of rail operators. Then, an adventurous operator may decide to trial this technology. But nonetheless, this is fairly unlikely, as rail slots are essentially priced by time occupied for the block, so it makes more sense to pack a train's worth of cargo into the reservation you paid for.