Please show the floor plan.

If you think you might want to paint those rooms a different color at some point, then I would add some drywall on the left to make it an actual cased opening.

All my openings between rooms have trim on them, as I wanted a consistent look throughout the house.

I agree with chispa. add enough to the left side of the opening to add trim

I think this depends on the style of the home. I have an MCM home with minimal adornment. The open doorways (no door) are not trimmed. This includes two openings to the kitchen, two openings to the foyer and openings at the ends of the hallway.

5 of the 6 openings are open all the way to the ceiling.

If I didn't own an MCM home, a modern or industrial home, but owned a more traditional home I would expect to see casings.

Chispa's solution is the right solution if you want trim and I think is a better look even if you don't want trim. It just feels a bit awkward with no wall around the doorway at all.

***** Disregard this ... The GC is fixing the issue so both can be cased. Thank you!

You did not talk to the General Contractor first??

Mark Bischak, Architect, Ready! Fire! Aim!

Generally, if an issue arises in a construction project, first discuss it with the architect. If there is no architect then discuss it with the builder. By circumventing the architect or builder, you will lose their trust and potentially damage the Owner/Architect/builder relationship; ramifications of which may be concealed and happen without the owner's direct knowledge. I state this for those reading this thread and belatedly to the OP.