The gemorah discusses each of these cases, IIRC (Megalgalin). From what I have learned, according to the Shittah of Torah Chasumah Nitna (that we are assuming), the question was one of applicability (meaning if the Halacha as will be tought should be applied at that point), not of knowledge.
That’s very difficult to say when the pasuk explicitly states that the manner of death penalty for the Shabbos desecrator was not explicitly stated.
The Wolf