So weird, phosphine is potentially the output of some life-based chemistry happening, but phophine has a lot of hydrogen. Hydrogen is something that Venus does not have a lot of. I haven't seen this addressed anywhere in the discussion yet.
Venus may not have a lot of hydrogen, but it does have some, especially in the form of water vapor. The amount of phosphine is also pretty tiny, about 20 parts per billion, compared to about 20 parts per million for water vapor.