This looks like an example of English influencing the classification. Do you agree?
Yes. This is also why I often wonder about the accuracy of the glosses. It seems consistent in the examples you post, but it's unclear what, for example, "nominalizer" means so a lot of this argumentation is circular, though it seems to be developing toward a good analysis.
There are three ways we could analyze such a structure:
1. By translation/function. It's not totally inappropriate to call this a complement clause in the sense that it seems to function as one from our English perspective.
2. Language internally: what distributional evidence is there for a relevant category of "complement clause"? None. There are nominalized predictes and unsurprisingly they can be used where nouns are used, even with case endings. The fact that a noun can be a complement is very uninteresting.
3. Universally/theoretically: if you subscribe to the idea that all languages share an underlying structure, we might wonder how these develop. Possibly these are "complement clauses" (or whatever
all languages have along those lines) being realized through the specific tools available in this language.
So the type of analysis really does determine the answer.
As far as I'd be concerned, for writing a descriptive grammar, I'd just call these nominalized predicates and note that they can appear wherever normal nouns can, with the same case endings. That's clear.
Are there any exceptions to that? If so, you may find a reason to discuss whether there is some kind of special "complement clause" construction. If not, there's no point-- you can leave the theoretical reasoning (#3 above) to someone else.
Edit:
I happen to be looking at a book by Aikhenvald and Dixon (2006; Oxford) called
Complementation so for a typological perspective that could be helpful for you.