I've tried printing the standard Esri topo-streets and topo-vector services, as well as the Esri OSM-vector service (added as a custom basemap).
If I capture the Web Map as JSON from the browser debugger and use it directly in the print service REST (services directory) form, I get the same result. I've tried the print with print services at version 10.7.1, both a standard print service and a custom service created in ArcGIS Pro. I've also tried it in the sample print service at http://sampleserver6.arcgisonline.com/arcgis/rest/services/Utilities/PrintingTools/GPServer. I understand vector tile printing was supported as of 10.6.