So it’s ok to assume that utm_to_point is also expecting the coordinates reversed. But utm_to_point takes a UTM object, and not an array.
Anyway, I converted UTM to latlong and then from latlong to point:
pointll = pointutm.to_latlong
point3D = model::latlong_to_point([pointll.longitude, pointll.latitude])
and it worked! Also on the complete set, and it matched perfectly.
Thank you for the help, and it sure looks like there is room for improvement in these methods.