Seems from other comments[0] that the first indicators of these moving phosphene regions were detected a century ago, which would seem to rule out even rapid Soviet contamination?
So not only do we have no good explanation for phosphine, we do not have a good explanation for the unknown absorbers. Well, we do have one good explanation although it seemed unlikely and that is life. Given that this is second effect that could be explained with microbes I feel it adds that much more weight to the theory.