The quote is hinting that in that skin's universe The Institute was destroyed, indicating it exists in the canon universe.
Lore on the Summoners and The Institute in the near future?
Edit: After I posted this I saw the other interaction with the warden skins regarding the League too, I'm inept and can't add another link though...
What does a non-canon skin talking about another non-skin have to do with the canon lore. Without counts that Riot said multiples times that the Institue of War and Summoners were comepletly deleted from the lore.
Considering that he travels through multiple timelines and universes it means that the institute exists in some universes(or at least existed in the past).
The main canon doesn't necessarily belong to those universes.
Warden vs Marauder is actually Protectorate vs Magelords which is what then ended in the creation of the Institute of War and the League of Legends and it's now canon in alternate universe.
It would be cool if they made that real in some skin universe etc.
Some of those lines are great, the obvious reference to Bloodborne in the dark water skins is nice.
