Question

The source for Netivot HaMishpat in section 234:3, that one who unintentionally violates a rabbinic prohibition has committed no transgression, is in today’s Daf Yomi, Eruvin 67b:
There was a certain baby whose hot water spilled out. Rabbah said to them: Bring him hot water from my house. Abaye said to him: But we did not make an eiruv. He said to him: Let us rely on the joint alley partnership. He said to him: But we did not make such a partnership. Let us tell a gentile to bring it to him. Abaye said: I wanted to challenge the Master, but Rav Yosef did not let us, for Rav Yosef said in the name of Rav Kahana: When we were in the study house of Rav Yehudah, he would say to us: In matters of Torah-level law, we first raise an objection and only afterward act; in matters of rabbinic law, we first act and only afterward raise an objection. Afterward he said to him: What did you want to challenge the Master with? He said to him: As it was taught: Sprinkling is a rabbinic prohibition, and telling a gentile is a rabbinic prohibition.

I have not been able to understand this. After all, the Talmudic passage is talking about there being a halakhic decisor on a matter of rabbinic law, so it does not make sense to call this an unintentional rabbinic violation, since this is not a mistake about the facts but about interpretation.
And as proof, Abaye himself corrected Rabbah on the facts, even though they were matters of rabbinic law—for example, that there was no courtyard eiruv and that there was no alley partnership here—and Rav Yosef did not stop him over that, because that really was a factual mistake. It was only when he wanted to discuss Rabbah’s actual permission regarding telling a gentile that Rav Yosef silenced him, and indeed Rabbah later answered him that one must distinguish between a rabbinic prohibition that involves an action and a rabbinic prohibition that does not involve an action.