Question

In one of the Rabbi’s lectures, the Rabbi mentioned the Ran in tractate Nedarim, who brings a practical difference for a certain case: that if a nazirite made a stipulation such-and-such, then the stipulation takes effect.
In Sanhedrin there is a Tosafot of Rabbeinu Peretz that gives this answer to the question why the Talmud discusses how close an ox had to come to Mount Sinai in order to be judged, and this is how Rabbeinu Peretz answered.
But in the lecture the Rabbi did not agree with that. Can the Rabbi explain again why this is not called a practical difference?