If only there was some obvious and easy to discern explanation for the discrepancy.
Either you're joking and reenforcing the idea that Polygon is in MS's pocket is entirely illogical [which it is] or I'm missing something.
I honestly don't mind what polygon thinks is the GOTY. That is subjective like anything review-oriented and they are certainly entitled to their opinion as is anyone else but what I do find somewhat surprising is the clear acknowledgement that their number system for reviews is obvious bullshit. I personally despise the numeric rating system that modern review oriented gaming journalists find necessary in order to validate their reviews [this need is of course the fault of publishers desires for "objective" measures of critical success] but I hate inconsistency and find a lack of follow-through more annoying. Furthermore I find Polygon's system even more infuriating as its not up to the actual reviewer but a panel of editors to determine the "score" based off of the actual review written by the reviewer.
It is fairly obvious what happened in this case. The editors at Polygon viewed either TLOU or the reviewer's review of it at some "7.5" level. That is perfectly fine I have no problem with people's opinions. Not everyone is going to like a game, no matter what it is. Someone out there dislikes pong, someone dislikes tetris but my issue is Polygon clearly backtracked without trying to admit to backtracking. They realized the general sentiment for TLOU was praise and love etc. etc. etc. and thus realized they had to put it on their GOTY list or face more rage from the internet or more derision at their style of journalism or whatever backlash they believed such an action would warrant. It is poor journalism to backtrack on your own entirely subjective assessment of something simply because other people seem to like it more than you do.
For instance if the review numbers were to be taken at face value then the list should be something like this [albeit I doubt TLOU would even place]
10. The Last of Us - 7.5/10
9. Kentucky Route Zero - No review that I could find - ?/10
8. Super Mario 3D World - 9/10
7. Brothers A Tale of Two Sons - 9/10
6. Tearaway - 9.5/10
5. GTAV - 9.5/10
4. The Legend of Zelda: A Link between Worlds - 9.5/10
3. Bioshock Infinite - 10/10
2. Towerfall - No review that I could find - ?/10
1. Gone Home - 10/10
And that would make logical coherent sense. It would be rational. At least compared to the actual ordering and review scores
The only conclusion I can draw from this GOTY list is that either Polygon are entirely incompetent and inconsistent when it comes to review scores or they pick the best game of the year with other metrics than "how good of a game it actually is"
In either case I have no desire for that type of journalism. It is lazy at best, downright disingenuous at worst