Modifying an ArcGIS Survey132 Connect form to add a new option on a select_one question, makes survey results with this new option appear with the name of the choice instead of the label.
According to the following ArcGIS Survey123 documentation:
https://doc.arcgis.com/en/survey123/desktop/create-surveys/updatesurvey.htm
When modifying the choices for select_one questions and republishing the survey, ArcGIS Survey123 Connect displays a summary of the changes and gives the option to decide whether these changes should be applied to the coded value domains in the feature layer.