I guess all I'm saying is that in addition to other evidence, other indicia—the person swerving, the person having glazed eyes, the person perhaps even saying that they've had a couple of drinks—if, for whatever reason, the crown wasn't able to proceed on the 253(1)(b), I don't see why the crown wouldn't then be able to use this information or evidence to support the 253(1)(a).
I take your point, though.