Is the main reason the manual goes on about it being last in the chain is for when it's sidechained by the whole mix, i.e. riding to the the vol stable relative to the entire mix? No point doing this halfway through the vocal chain..
When you're not using it for this I'm less clear
(i) how it's different from / not a compressor (which all just ride the volume to an 'algorithm', rite, sometimes with some added goodies (sat. etc) that are nothing to do with compression but about emulating old gear?)
(ii) why there's a reason it should go last (shoot me down here, but a nice level vocal performance into a nice characterful compressor, isnt that not too similar from a pro singer into an old piece of hardware, if you put the VR in the middle i mean? [edit: this isnt a "plugs will make me pro!" point, more that the workflow with plug in the middle could be justified on the basis of it being a tiny step towards how it might normally work on a good day in a pro studio?]
Should say i love the VR, i'm an amateur but i feel it's really helped me with the all important vocal sweetspot vol on the track....