Honestly, at this point I can no longer tell whether you're misinterpreting or misrepresenting the conclusions. I'll make an honest attempt to argue, nevertheless.
"Static type checking" and "unit testing" are two concepts. There are numerous concrete implementations of these two concepts. The former is implemented in several languages, including C++ and Java and Haskell. The latter is implemented in several frameworks/tools, such as TestNG and PyUnit.
The article concludes that unit testing, as a technique for discovering and/or preventing defects, cannot wholly replace static type checking.
Apart from mentioning the concrete implementations of abstract techniques that the author used, the article does not conclude anything about the benefits of using specific languages, frameworks or tools.
What you have claimed so far is that:
1. there is a "hidden assumption is that all static and dynamic typing are created equal, i.e., since Haskell is statically typed and Haskell appears to have caught Python bugs that unit tests did not, therefore Java will catch bugs in a Ruby codebase, C++ will catch bugs in a JavaScript codebase, etc."
If anyone jumped to this conclusion, it was you. The only thing I can conclude from the article is that static typing checks such as those implemented in Haskell catch bugs that were not caught by unit testing logic such as that used in Python projects within the study. To conclude anything more I would need the data not present in the article, such as exactly what types of errors we caught or missed, etc.
2. the conclusion of the study "makes an unwarranted equivalence of all languages that have 'static type checking'"
It doesn't. The conclusion about the static type checking vs. unit testing might not be backed by enough solid data, but the conclusion makes no claims about languages, beyond specifying which languages were used in the study.
3. the claim that "this benefit applies to all languages with static typing" is "precisely what" the conclusion "says".
No occurrence of any phrase even remotely resembling the quote can be found in the article. Saying "this is precisely what it says" means "you'll find that phrase or one very similar to it in the text". Maybe you were trying to claim that "this is precisely what it means", but it's definitely what it "says".
All in all, the sweeping generalization about the concrete languages was introduced by you. My guess is that this is because you were, like me, frustrated by the vagueness of the article. I would have loved seeing more concrete data. Saying "X types of errors were found" is not as good as saying "the following types of errors were found" and that's just the start.