Their discourse effects are similar to biased questions in that they seek information from the addressee while conveying that the speaker already have certain expectations.
Different researchers come to different conclusions about whether the two kinds of rising declaratives have the same semantic content, and some analyses cover only one or the other category.
In such accounts, their respective discourse effects arise from the interaction between these denotations and pragmatic reasoning or conventions of use.
For instance, Westera (2013) argues that rising intonation conveys that the speaker isn't sure whether their utterance is in accordance with Gricean Maxims.
On this account, all rising declaratives have the same semantic content but end up with different discourse effects depending on which maxim the speaker worries they are violating.