The context makes it like saying life jackets won't keep you from drowning in a boat. They will if the boat starts sinking.
That is not a lie. What you are doing is twisting the first statement into the second to call it a lie.
They were trying to keep it simple, and while I agree that they should have said it was for medical professional use first I can see why they would leave it out to avoid panic buying since so many people are idiots.