I'm not denying its a clever way to create a bus, and I'm not trying to give Ludwig flak about it. I just want to know why it is worth the effort when we already have busses built in that do exactly the same...
The only advantage I can see is being able to place the bus right next to the group of tracks that are being summed: ie. vox1, vox2, vox3, vox bus, guitar1, guitar2, guitar3, guitar bus. But then you're mixing your busses in with the tracks, making them harder to find, harder to compare bus levels, etc...
I still don't see an advantage.
There is an advantage to having all your busses in one place however. With your main drums, guitars, keys, vocals, FX, etc. busses next to each other you effectively have a sub-mixer that gives an at-a-glance overview of what your mix contains, what is playing and how loud relative to the other sound groups, etc.
I realise that is a work flow preference.