Me and a buddy had this happen to us (group of 2), where a WSP officer was coming towards us with RADAR on, across a median, with my buddy in the lead. He saw the cop and slowed down quick, but I was still passing a car, so I passed him as the cop car went by going the other way. We were both on blue bikes, and the cop pulled him over because he was closest (and in the rear). I slowed down but kept riding, so the cop pulled back out and came after me. Then my buddy pulled in behind him, and he motioned for him to come around front.
I figure if they want you to pull over, they will let you know. Maybe a LEO will chime in with additional feedback.
Given that two motorcycles in staggered formation provide different targets of different distance, with similar RADAR profiles, I've never felt it's reliable to use in that scenario. He didn't write us up, since he couldn't prove which one of us was speeding, and the fact that we confused him when I took the lead. Plus there were other cars behind us, one which I thought was coming up fast.