Out of 91 users on REI's website 34 have complained that they have been unable to send messages. This works out to roughly 30% chance that your message didn't make it out. The statistics are even worse for the Spot Smartphone unit. Are these the kind of odds you want in a real emergency?
Whoever wrote that isnt very good at statistics. Unless out of the complaints, the device fails to send messages 100% of the time, all it means is that 30% of users have experienced message failure at one point or another.