I am not familiar with this specific situation in the US but there are also similar topics in other parts of the world (with civil airborne radio-altimeters as a victim). It might seem odd to talk about interferences while 5G is in its dedicated band far away from radio-altimeters spectrum (> 4.2 GHz), however you have to understand there are 2 phenomenons to take into account :

1°/ transmitter unwanted emissions of 5G (i.e. how much out-of-band/spurious emissions "leak" outside of the 5G band i.e. above 3.8 GHz). This is most likely a negligible issue here even though there are still uncertainties whether the antenna pattern of AAS remains the same in-band and in spurious emissions

2°/ receiver blocking of the radio-altimeter (i.e. even if 5G emissions were perfect, the victim receiver can catch energy from other bands if it doesn't include a proper filter) : this is most likely the main issue here -> from my understanding, those airborne equipments have poor filters (the antenna limited passband probably helps a little bit which is why this blocking phenomenon did not happen previously with 4G in lower bands, but apart from that there is probably a low selectivity with regards to adjacent bands)