Everybody can write in a wiki. That is not serious source. What the wiki is referring to is an interview with Neil Druckmann. AFAIK that interview was the one after the first trailer at PSX. Would be too long to summarize everything. Here is the Youtube video:
https://www.youtube.com/watch?v=gF1EQAtaZEo
In that interview he simply says that he told Ashley Johnson about the story of the second game back in 2014. But thats it.
Now take a look back:
- After Left Behind the whole studio was fused together to one single group. Everyone was focusing on Uncharted 4 and some people on TLOU:R. They even stated that.
- After Uncharted 4 launched the main focus went to The Lost Legacy.
- At PSX it was said, that the game is in "really early state of development".
- Naughty Dog also stated in an interview, that most of the people are working on The Lost Legacy. They also mentioned that The Last of Us Part II is not in full production yet.
- They said full production of Part II will start as soon as TLL is finished
- In the credits of The Lost Legacy they have an category that is called "Special thanks to the kennel". In this category around 30 people are listed. In other words: These are the guys and girls that worked full time on Part II (can be confirmed by checking their Twitter profile etc.) while the rest of the team was focused on TLL.
And then there is this interview. The interesting part starts at 0:20
https://www.youtube.com/watch?v=ZUqlgfXbyG4
Other sources:
https://gamerant.com/last-of-us-2-development-start/
https://segmentnext.com/2017/04/01/naughty-dog-focus-on-the-last-of-us-2/
https://www.gamepur.com/news/27338-last-us-part-ii-development-update.html
https://playfront.de/the-last-us-part-6/ [german]
https://www.dailystar.co.uk/tech/ga...The-Last-of-Us-Part-2-Shaun-Escayg-Arne-Meyer