It’s all fine and dandy, until you realize that the secondary extruder suffers from constant under-extrusion. So it prints supports that are more brittle (due to being weak from under-extrusion, and bad layer adhesion) and break easily.
If had many many prints break mid-way, because the bowden-printed supports simply broke mid print due to bad (under-extruded) layers somewhere mid-support, which made it structurally weak once the main extruder (with higher speeds) tried to print something on top of them.