You might be surprised just how good a cell phone mic (or in the case of a modern phone, mic array) is. They are very carefully tested for frequency response, THD, dynamic range and other artifacts on every phone made. There is an immense amount of DSP going on to perform beam steering (limiting room reflections) and FR corrections to a point no studio recording microphone can get within the same zip code. Multiple sample conversions and internet transmission will have a much greater effect. You could put a pristine RCA 44 or U47 up there and you'd be hearing those mics, using the cell phone is letting you hear the amp.