I've already sent an e-mail to WCI asking them the very question you raised, Peter. I haven't received a response, yet.
One on line lab that I've used is Elco, which also has a profile solely for soft proofing. Elco is very clear that, when using their profile for soft proofing, to set it up with perceptual and no BPC. Perhaps Elco just converts all files with that one setting. In any event, with my photos without gamut problems, that soft proof and the actual prints match my original aRGB file (viewed on my calibrated monitor) very closely.
Dan, as you now probably realize, I'm struggling with what settings to use when soft proofing so that my soft proof corresponds to the actual conversion done by the lab. It's not a question of what looks better. It's what matches what the lab will do, since I don't make the actual conversion, the lab does.