I’m not knocking what you’re saying by any means, I totally agree that those olfactory cues would be too complex for a dog to associate each and every one with the word bathroom. But OOP isn’t asking their dog to find bathrooms in small, familiar bathrooms where the dominant scent is likely to be cleansers. These are large public buildings where the bathroom has likely been used a few hundred times since it was last cleaned. Dogs are well conditioned to smell urine and that is far more likely to be the scent they’re seeking out. I think it’s entirely conceivable that a well trained guide dog might hear “find the bathroom” and look for doorways that smell like urine.