Dimension bug with two head tubes

I've just found some surprising behavior in the top tube miter dimensions when designing a bike with two head tubes (a cycletruck style cargo bike). 

The angles shown on the dimensions didn't look right, so I put together a frame with simple angles to really show what's going on. The front head tube is at 74 degrees. The middle head tube is 85 degrees. The top tube is horizontal, so the front top tube miter should be 95 degrees. 

But the front miter dimension shows 16 degrees! Which means it's using the front head tube angle to compute the top tube miter dimension!

Check it out:

These are the dimensions I'm using:

For now, I'll switch to using the "top tube front edge angle" instead of the "top tube front miter angle". But it would be good to have these dimensions changed to use the middle head tube when it's present. 

I'm glad my angles were different enough that it looked visually wrong to me! If my two head tubes were only a few degrees apart, I probably would never have noticed!

Thanks so much!