Thank you. It took a moment to process the concept, but I think I get it. Makes sense to me anyway. But let's check...

The more a seat tube is angled backwards, the lower the tail end of the FD cage sits in relation to the the chainraings, and so it doesn't have to pick up or lower a chain as much as it would if it were positioned directly above the bottom bracket. Correct?

In this case, the frame in consideration has a fairly upright seat tube geometry. Eisentraut touring frame with a 55 cm seat tube, and 54 cm top tube. Seems that in this regard, and without knowing the exact angle of this seat tube, the frame itself may present further challenge on a Vx front derailleur already tasked with a wider gear tooth differential than its designed for.