Audience library : Limited Segmentation capability means

[Umamaheswari_Yakkala]

I'm wondering if someone could help me understand audience library Cons.

Having dubts while going thorugh this article "Adobe Summit 2018 S712 - Audience Hacking: Get the Most from Adobe's People Core Service " 

what is meaning of  " Limited Segmentation capability" cons for Audience library?

what kind of limitations ?

Does anyone could help me with this limitation for Audience library?

Thanks a lot