So the two uses appear quite far apart in the frequency domain. Do signals get sent out on the wrong frequency or something? What does it mean to interfere? And, assuming something bad is happening, why?
With potentially high gains from beamforming, both the fundamental mode and spurious emissions from 5G radios exceed the safe interference limits for the current RA specifications by at least 10 dB.
Radio towers (sites) have widely varying quality control of their tenant's installations. Other transmitters can mix and amplify signals from other carriers without well designed and maintained RF filtering on each and every antenna. The more transmitters at a site the more carrier frequencies that can contribute to the mixing, and the more opportunities for poor or broken RF filters. At some busy sites there is almost nothing you can do to prevent this. Anything on the tower that acts like a diode can cause mixing, even without being amplified by another transmitter.
This usually just harms other receivers at the site however. But an airplane flying close by could theoretically be affected depending on how close it is.
N.B. as far as I know, the portion of the C-band that's in question was allocated for satellite downlinks; uplinks were over 6GHz. With that in mind, there is indeed a Big Difference between a satellite in orbit radiating downwards, and a 5G beam forming installation on the ground potentially radiating upwards.