the remark about ua can perhaps be omitted here because it is confusing and disrupts the line of thought.
alternately, it could be reformulated as:
The univalence axiom, like function extensionality, can be seen as an ``extensionality'' property of the identity type; its incompatibility with the reflection rule means that intensional type theory with univalence is, in a sense, even ``more extensional'' than extensional type theory (an unfortunate clash of terminology).