The new frame builder relies more on stack and reach for the front triangle. It still doesn't directly reference the top tube, that might be the next version. It seems like this outputs the correct geometry though, the only thing I'm not sure about is the front fork length and angle in relation to the head tube.
Some examples; first an Ibis DV9:
Then an Ibis Hakka MX; it doesn't look quite right...:
And an OPEN One+
Hopefully these examples make it more clear that the displayed head tubes are more of a suggestion for placement. The key information is locating positions and key components.
Since the tube profiles can be changed, additional guide curves plotted, etc. This makes a good virtual design tool for then dissecting and assembling out of foam. I'm going to average a few more designs and then start on start on actual design for myself to produce in foam. I'm waiting on some bandsaw parts on the physical side.