There is no way to build a perfect filter. 5G equipment will emit outside of its assigned spectrum and radar altimeters will receive signals from outside their spectrum. The next important variables are the power of the transmitters and the effectiveness of the receiver's filters (and the sensitivity of the receiver). Radar altimeters have been doing their thing for decades because the previous uses of that band had much lower power.
Your analogy is a great demonstration why reasoning-by-analogy fails, by the way.
Your analogy is a great demonstration why reasoning-by-analogy fails, by the way.