This seems to be the largest weak point in the study that I found. @Paul.B.Rimmer how did you account for the fact that temperature can shift absorbance spectra?
Given that there is such a wide range of temperatures on Venus, shifting spectra for all species, how do you filter out something that absorbs that band in a temperature range outside what you considered? I imagine that the sharpness of the peak does give you some support. Even if the absorption peak is relatively stable to temperature for PH3, the absorption of a confounder chemical may not be temperature stable.