I really hate that marketing. As it's very loose in definition and often followed with "this can allow firing missiles etc"
If one stick to say, K.Barton's "Radar System Analysis and Modeling". Page 449 have this :
View attachment 146756
NO AEW radar will meet this criteria for missile or gunfire control. APY-9 may still have mainlobe width of some 7 Degrees which, well not a "fire control grade" as per K.Barton's book above. Even fighter jets, typical fighter radars have mainlobe of about 3-4 degrees. Very rarely 1 Degrees and that is usually for ground attack as narrow beamwidth helps in getting clutter away and to get better resolution in real-beam mapping.
The better approach is perhaps should be SNR as probability of detection and tracking relies on SNR. Radar "lock-on" or Tracking is typically initiated at very high SNR condition e.g 24 dB. Which correspond to 90% PD for Swerling-1 Target. Also the angular accuracy can be calculated more definitively. This approach is more "frequency agnostic" as you can do this in any frequency.