A legendary sermon.

Hello Rabbi.
Sometimes I find a disagreement in the Gemara regarding the requirement of a particular verse, but one of the conditions requires it for matters of halakhah and another requires it for matters of agga. And that is a bit strange to me. Isn’t the requirement of verses intended for halakhah purposes only? And furthermore, if we have the ability to conduct a halakhic sermon, doesn’t it reject an aggadic sermon? And in general, what does this say about the tools of the sermon? The aggadot claim something about reality and there is no authority for the Sages on this. Do the tools of the sermon assist in claims of fact and not just halakhic criteria? And if so, then just as the aggadot are not necessarily correct, neither are the halakhic teachings, since they are derived from the same source.
Thank you very much.