Answer

It seems obvious to me that they should offset. In fact, what they really should do is take a Knesset member’s position into account even if he is not physically present in the plenum, and that’s it. The obligation to offset is not an interpersonal obligation between one person and another, but an obligation to the people who sent him. It is not meant to accommodate the Knesset member who has to be absent, but because the law is supposed to reflect the true majority of opinions in the Knesset, not a majority created by parliamentary maneuvering.