At a glance, these questions may be mistaken as duplicates. However, I, and a few others, have shown that the "duplicate" question is actually not a duplicate.
The latter question asks a simple question: "If I switch my buddy Pokémon A to buddy Pokémon B, regardless of species, does total distance reset?"
The answer is no, the total distance is reset.
The question you are attempting to mark as a duplicate asks a different question: "If I switch from buddy Pokémon A of species X to buddy Pokémon B of species X, is the total distance the same across both of them, as they are both species X? Or is it different because they are Pokémon A and B?"
The answer is no, the total distance is dependent on whether it is Pokémon A or B, not on if it is species X or Y.
In your last comment on the question, you made a remark, saying "if I ask the same question about switching from Pidgey to a Rattata, would it be a duplicate?" The answer to that question is absolutely, yes, it is a duplicate. However, by adding the distinction of different species, you are asking a different question that is covered by the one you're duping to. None of the answers in that question answer the question asked in the "duplicate" and people searching for an answer for the one you want to mark as a duplicate would not find the information they sought by only seeing the question you want it to be duped to.
In general, however, I believe we are supposed to not mark things as duplicates if they do not help the original asker. In this instance, the duped question would not help someone with the same question as the dupe. See this meta post.