I take your point (or should that be vertex?), however...
It's almost immaterial that your terminology is "technically correct".
If (and it is an if - I don't have any stats to make the point one way or the other, so I'm posing it as a question) a large percentage of your user base find your terminology confusing then this would still fall under the category of 'poor usability / user experience'.
In my mind, things like this make me think of yEd as "quirky" and "unintuitive" rather than "correct".