To the best of my understanding, Kaufmann is absolutely right.
Nietzsche postulates "the preparatory task of making men to a certain degree necessary [...] calculable."
- No reasonable interpretation of the syntax will afford you the translation "it is necessary to make men uniform etc."
Jene Aufgabe, ein Thier heranzuzüchten [...] schliesst [...] die nähere Aufgabe in sich, den Menschen [...] zu machen.
What we have here is the logical, presuppositional pairing of two instances of "Aufgabe", a noun that typically takes (requires) an infinitive clause. The symmetry extends to the dependent clauses themselves and their semantics: "ein Thier heranzuzüchten" and "den Menschen [...] zu machen".
Note that "die Aufgabe" requires a dependent clause, just as the infinitive clause "zu machen" requires a governing (verb, adjective or) noun such as "Aufgabe".
(1) Ich befehle, den Menschen... zu machen.
(2) Es ist notwendig, den Menschen... zu machen.
(3) Wir haben die Aufgabe, den Menschen... zu machen.
(N) die Aufgabe, den Menschen zuerst bis zu einem gewissen Grade nothwendig, einförmig, [...] berechenbar zu machen.
Syntactically speaking, the natural reading of (N) is to connect "die Aufgabe" with "einförmig, [...] berechenbar zu machen" directly, as in (3). If you let "notwendig" step in to govern the "zu machen" clause, as in (2), you would take away the dependent clause that "the Aufgabe" requires and leave it dangling. This makes it a very unlikely reading of (N).
Instead, the noun Aufgabe governs the infinitive clause zu machen + an array of attributes that are all on a par: "making men necessary, ... predictable".
Syntactically speaking, Kaufmann is right.
- Semantically (and philosophically) speaking, Nietzsche's connecting "nothwendig" with "regelmässig" and "berechenbar" makes good sense and has a long tradition behind it. All these attributes are closely related and somewhat synonymous, even "necessary".
First, while you seem to read "nothwendig" as implying an inflexible, exceptionless, absolutely deterministic necessity, note that in Nietzsche's passage, "nothwendig" is qualified: "bis zu einem gewissen Grade".
The individual is to some, even to a large extent, determined; that is,
not absolutely free, but rather (somewhat) controlled by its habits, influenced by its education, conforming to certain rules. All this makes it likely to behave a certain way, hence predictable ("berechenbar").
And this is Nietzsche's philosophical point here: raising men who conform to the expectations of morality is akin to creating trained animals that are influenced, somewhat controlled, by behavioural laws (in fact, he calls it "ein Thier, das versprechen darf").
This view of animals is in line with a broadly Cartesian, or Kantian, tradition that views the "brutes" as determined and bound by the laws of nature (and nurture); to some extent necessitated ("nothwendig") to act by those laws, or rules ("regelmässig"), therefore uniform in their behavior ("einförmig").
(The more extreme view would be Descartes' assumption that animals are just machines and their behavior is strictly necessary and deterministic; Nietzsche's contemporaries in philosophy and the life sciences would soften this assumption but still go with a view of behavior as somewhat deterministic: "bis zu einem gewissen Grade nothwendig".)
There is no need to doubt Kaufmann's translation, which (at least in this passage) is spot on.