Hello,
thanks for the skinparam linetype option. I found a bug that with version lower then 2.36 of graphviz the ortho is redered equaly as polyline.
Please see
https://avono-support.atlassian.net/browse/PUML-179 for details.
So maybe it is a bug that can be fixed on code level (code bug) or mentioning the minimal requirements in the documentation (docu update request).