As pointed out by Kingshorsey, your analysis of this sentence is correct. Unfortunately, the Wikipedia article classifies your example from Nepos under the wrong descriptor ("The gerundive after ad can also be used to express purpose"), which is only valid for the example above yours in this article: i.e. L. Septimium tribūnum militum ad interficiendum Pompeium mīsērunt. [NB: the very same descriptor says that this usage is shared with the gerund, i.e. the gerund after ad can also be used to express purpose. This is correct for examples like the one mentioned below in the article (e.g. idōneam ad nāvigandum tempestātem 'weather suitable for sailing') but should not be interpreted in the sense that the syntactic distribution of gerunds and gerundives when preceded by the preposition ad is the same: e.g. the preposition + gerund + object construction in L. Septimium [ad interficiendum hostes] miserunt is not correct in Classical Latin (cf. the correct gerundive construction: L. Septimium [ad interficiendos hostes] miserunt); see this post for further discussion].
As for the examples provided by Kingshorsey, it seems to me that it is not obvious that your example from Nepos, where a non-argumental (i.e. adjunct) "purpose" construction (cf. Kingshorsey: "the gerundive as object complement of hunc is equivalent to a purpose clause") appears to be involved, is to be assimilated to an example like Caesar pontem in Arari faciendum curat, where the gerundival clause does have an argumental (i.e. non-adjunct) status. See this previous post on how many types of "predicative gerundives" are in Latin; in particular, take a look at the last information in this previous post: "Pinkster (2021: 231; fn. 268) points out that the causative verb curare lacks a final interpretation". In contrast, note that this "final interpretation" is not obviously excluded in your example from Nepos. So, after all, these two examples could be provided with different syntactic analyses. As far as I know, this tricky (but very interesting!) issue of Latin syntax remains to be solved, i.e. you'll find some people who are happy to unify the apparently different types of so-called "predicative gerundives" (let's call them "the lumpers") and others, "the splitters", who aren't.