The general idea of the badges is to encourage behavior that is positive to the community.
Now, you apparently do not need the encouragement regarding this behavior (also upvoting other answers where one has one by oneself, as opposed to seeing them as "competition"), which however you seem to agree is a positive or even natural thing to do. And, it might be that on MO this is in general less relevant, since it is not so common that there are very similar answers given to the same thing, however it can also happen.
In particular in such situations there is an effect that not rarely one of the answers "wins" in the end and gets significantly more votes than equivalent ones (on the grounds that it is ahead early on, and then some seem to only upvote one/the first they see (often sorted by votes), answer giving some piece of information and the gap widens.
So, I think in a scenario where one answers in parallel with somebody else about the same thing, then sees the other answer, and then upvotes it. Then by doing so one likely actually harms ones prospects of getting points out of ones own answer (and also the accept).
This is I think the scenario they mainly had in mind. As said on MO this is not so frequent but I think on other sites it happens all the time. (And such situations can cause friction; math.SE seems to have had various problems arising from such things.)
And depending on how this badge is implemented precisely; if it is exactly as written, that is the number of answers one upvotes counts (and there is no exception for CW) then anybody being in some of big-lists could trivially get it just voting around there a lot.
However, that one can also get the badge in an "absurd" way is true for many and specifically for thos badges based on participation/volume. Say, I could get a fanatic badge, while never contributing anything, the ones based on votes mindlessly up-voting whatever I open, the ones based on edits doing irrelvant edits and so on.
This might be a downside of all these badges that if somebody really wants them they might do more harm than good if somebody does what is asked for in an unreasonable way.
However, for the ones in question here, I would say somebody actively trying to get them will do little harm in doing so (opposed to the situation for the review badges mentioned in a comment), while the behavior encouraged is positive (and you seem to agree with this).
In that sense, I think these badges are relatively more reasonable than some others we had all the time.