You might as well stop looking for objective truth here, because there isn't any. Before volume/expression pedals existed, if you wanted to incorporate volume swells into your playing, you were stuck doing it with the volume knob on the guitar... the equivalent of placing the volume block before the amp model. It's a perfectly acceptable way to do things... as is placing it after the amp and before any effects. It merely depends on one's personal preference, and what you're actually trying to accomplish. Some guys just want to use it as a boost, or as a quick-access master volume control on stage. In those cases, you'd want the volume block dead last in the signal chain. It's all fine if produces the end result that you want/need.
The notion that there's a "right" and "wrong" way to do it, is ridiculous. As for their choice of default volume block placement in the factory patches.... they have to stick it somewhere, and like most things, no matter where they put it, somebody's gonna get a wild hair.