I think this question represents a misunderstanding of the linked article, and in any case of the specifically US doctrine of fair use.
Fair use is always based on a part of a copyrighted work copied without authorization. If there was authorization, there would be no need to resort to the defense of fair use.
The article discusses the commercial use of short sections of musical works used for commercial purposes. It points out that the idea that any use of an excerpt of less than 30 seconds is permitted is a myth. In this it is correct. While the amount of a copyrighted work used is one of the four factors to be considered in deciding wither a use is a fair use, it is not the only one, and no specific amount is always permitted. In Harper & Row v. Nation Enterprises, 471 U.S. 539 (1985) The US Supreme Court held that quotes amounting to about 3-400 words from a 500-page book were an infringement, and were not a fair use, because they were the "heart of the book".
The linked article says that one should ask "Was the work obtained from a legal source, in a lawful manner?" and asserts that "taking a copy from an unapproved source invalidates fair use." Nothing in 17 USC 107 says this, and I don't know of any authoritative source for such a statement. The article also says that "Commercial, for-profit use is not fair use, while commentary or criticism may be." This is simply incorrect. While a commercial purpose tends to weigh against fair use, it does not preclude it, and commercial use has been held to be fair use in some cases. Even in the case of Harper & Row v. Nation Enterprises linked above, fair use was seriously considered, and was not denied simply because the use was commercial. No one o0f the four fair use factors is final taken alone. I do not think the linked article is a reliable guide to US copyright law.
In the case described by the question, an unreleased game has been distributed without authorization over the internet, and reviews written based on that unauthorized copy. Whoever copied the game committed copyright infringement, but a suit might not provide substantial damages unless actual economic harm could be demonstrated. (And, of course, the identity of the infringer would need to be proved.) But a review based on such a leaked copy would not necessarily be an infringement. If the review described the game, but did not quote any of its dialog or other text, and did not reproduce any sounds or images from the game, there would be no infringement. If the review did quote from the unauthorized copy, the usual fair use analysis would apply. The fact that the copy had been unauthorized would not determine the outcome.
Fair use is defined by 17 USC 107. This provides:
Notwithstanding the provisions of sections 106 and 106A, the fair use
of a copyrighted work, including such use by reproduction in copies or
phonorecords or by any other means specified by that section, for
purposes such as criticism, comment, news reporting, teaching
(including multiple copies for classroom use), scholarship, or
research, is not an infringement of copyright. In determining whether
the use made of a work in any particular case is a fair use the
factors to be considered shall include—
(1) the purpose and character of the use, including whether such use
is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to
the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of
the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding of
fair use if such finding is made upon consideration of all the above
Note that criticism is one of the specified purposes for which fair use is designed, and an unpublished work is still subject to fair use. If the review quoted so much of the game that the potential market for it was harmed, that would weigh against fair use, but it is hard for me to see how a mere review could do that to an interactive game.
(17 USC 107(4)) is normally applied when an infringing copy serves as a replacement for the authorized version, and sales are lost as a result. I suppose it might be argued that a bad review that was a direct result of an infringement came under this provision, but it is a strech at best, and US First Amendment considerations would tend to prevent such a ruling.
In short, it seems unlikely that any normal review would be an infringement, and that the game was leaked would not make it one.