Beerus vs. SSJ3 Vegetto scenario...

[Polyphase Avatron]

I'm thinking that maybe different types of ki need some experience to be sensed, for example after spending time around Kaioshin and Kibito and their fusion, and elder Kaioshin, Goku got a feel for learning how to sense their ki, but Beerus has a different type of godly ki that he never sensed before so he can't sense him, although with practice he or the other Z senshi could learn how to.