In Windows 10 Insider Fast Ring, Update to RS5 17754, Then do Store Update to update Skype and People to latest version.
Pinned contacts using People to taskbar. Open contact and select Skype, I find it can only send file and message, but there is no UI button to make a call as version 1803.
Here is the screen shot. On the left, it is RS4 (1803). On the right, it is RS5.
On RS4, the skype is 12.x. On RS5, the skype is 14.x. Is it a feature change on new version? It doesn't look like a good idea to remove shortcut button for call.