The first Red Flag is the idea that mushrooms are "simple" organisms ... they're not organisms, they're the fruiting body of an organism ... and thus an fairly advanced form of life as found on Earth ... just slightly below vascular plants in the Grand Scheme of things, here on Earth ...
The underlying fungus that produces mushrooms are (at a minimum) detritivores ... their food source is dead and decaying organic matter ... thus we need the whole suite of plant life as primary producers using photosynthesis to allow the fungus to grow and form their reproductive organs (the mushroom itself) ...
These mushroom producing fungi are land organisms ... and it took about 4 billion years here on Earth for such an organism even to begin evolving ... and the land surfaces here on Earth are far more suitable for life of any kind than the surfaces on Mars ... we've always had rain and rivers on Earth, the available water on Mars disappeared long long ago ...
Last item and I'll quit ... almost all the geology on Earth occurred in the presence of water ... roughly 90% of the geology on Mars occurred without water ... so this wouldn't be the first geological formation to be found there that has never been seen on Earth ... I'm thinking of the "blueberries" found many years ago ...