The article by Kotaku explains that Rocket League will be getting an update that adds a basketball gametype. The article ends with the writer rejoicing how, "I can’t even begin to describe how happy this makes me."
The Gamasutra article is how the rocket jumping in Rocket League came about. He goes onto explain that the design process of the game just happened to spawn the rocket jump since it was completely unintended and it was just the combination of different mechanics and the engine combined. Towards the end, he goes on and explains that the rocket jump and soccer gametype is why Rocket League has the longevity it does.
Gif taken from the article on Gamasutra. User who uploaded the gif to Gyphy was EssentialImpartialAsiaticmouflon
The article from Gamasutra is about the Design process of Rocket League's rocket jump. The article goes into how Rocket League became to be the Studio's previous works. Comparing that to the Kotaku article, it's quite different. The Kotaku article only talks about Rocket League's upcoming gametype which was teased on twitter (See below)
The Kotaku article talked about the upcoming gametype that had been teased which the Gamasutra article didn't mention. The article also ended with, "The hoop will be fairly low down and quite wide, which should make it a fairly accessible in terms of scoring. Defending though … well, that’s going to be a fun challenge." I find the Kotaku article to be more relaxed and open compared to Gamasutra's.
The article from Gamasutra went into detail about the design process with Rocket League. What I learnt from it is that the game was more built around one mechanic than a game's idea building the mechanics.