I can confirm that the selection is horizontal-only currently. Please feel free to cast your voice for vertical mode on UserVoice.
The lack of a public API for the selection is indeed a pain point and we'll try to address this in future releases.
Currently you can use setOptions for setting it:
var chart = $("#chart").data("kendoChart");
// No need for calling redraw in future releases and latest internal builds
Apologies for the caused inconvenience.
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI