I suspect they just redirect it somewhere else, probably since Qt does some of it's own argument parsing among other things, they just want you to do it "their way" instead of using printf() directly etc.
Or... came to think of it, isn't your GUI always a child process of main()?
Hmm.. I should know this since I wrote the Qt logging libraries for some companies.

If they needed that level of flexibility (multicast etc), it would've been easier just to use TCP/IP directly.

So, the problem is that the MTD subsystem does not have drivers for a bus that does not yet exist, most drivers maybe assume that you've connected it to GPIOs directly?
Obviously a new memory bus would need a new driver. But to make things simpler, you could just a have a tiny nor directly connected, to store the bootloader, kernel and a simple root.
Then when the kernel is up, you use the more complicated bus and filesystem, so you don't need to develop drivers for the bootloader as well.

But a block interface does not translate well to flash memory, that's why we lose so much performance and suddenly the thing may crash when there are too many faulty flash blocks.
So, is performance an issue when you scale ubifs to gigabyte sizes?