Survey123 relies on theArcGIS Online Export Itemcapability - at this time it does not have an option to select whether the field name or alias (which Survey123 populates with the label). One workaround would be to populate the bind:Esri:fieldAlias column when authoring a survey to provide a shorter label. Another way might be to export to fgdb first and then export to CSV from ArcGIS Pro or ArcMap.
I realize this is an old post but I too ran into this problem and I while I was not able to get either of the "bind:Esri:fieldAlias" or "export to fgdb" workarounds to work for me, I did find that "export to shapefile" worked (from which you can then export to CSV from ArcMap/ArcPro). I do find it curious though that if you "export to CSV" directly from AGOL then the display names (labels) get exported and not the field names.
