lmum
All railway stop nodes are present along the Haverhill Line, but they don't appear to be part of the MBTA Haverhill Line relation. (So, different than the other Boston commuter rail lines.) There was an effort to clean this up in 2023, but I'm not sure the Haverhill line got cleaned up. 

https://wiki.openstreetmap.org/wiki/Mechanical_Edits/JesseFTW/Fix_MBTA_stop_position_nodes

I don't know much about the rail line tagging structures. It would be great if someone who does could check the relations for consistency. 