פירוש על עבודה זרה 74:5

There are two problems with the last section of the Mishnah. First of all, in this case R. Yose b. Yoezer is stringent. Why then is this put in with the reasons that they call him “Yosef the permitter.”
Second, what he seems to be stringent about is actually in the Torah itself. This is not a rabbinic decree or law of any sorts. It is from the Torah.