True, but that’s on the ground and short range. There’s specific dialogue to show that it’s interfering with signals between space and ground.
SPOCK: I detect a counter-frequency emanating from the planet. It appears to be negating all scans, communications, and transporter signals between here and there.
Spock can’t even scan for life signs on Cayuga. The best they have is passive sensors like spectrometry.
UNA: Still trying to scan for life signs?
SPOCK: I theorized I might be able to find a frequency gap through the interference field, but I have not managed to discover one yet.
UNA: Spock, I don’t think anyone’s alive over there.
SPOCK: Spectrometric analysis suggests there are still pockets of oxygen on board. It is possible someone could have survived.
That’s why they had to do a visual confirmation and discovered Cayuga’s sickbay had been blown away.