"Arms sold 1.18 million copies between its June release and late July."

https://www.nintendo.co.jp/ir/en/finance/software/index.html

As of June 30th, Arms sold 1.18 million in 2 weeks. It launched June 16th. This means that even if Splatoon 2 theoretically killed Arms legs it doesnt matter because the information theyre using is from before Splatoon 2. Essentially they're saying that Arms sold1.18 in a month and a half - when it sold that in two weeks
 
This is a case of kotaku literally looking at the day sales articles about Arms were posted, and not reading when thr sales data was collected. An all new low for gaming journalism.

Most of the early commentors seemed to have not read your post. I will say that I am a bit concerned Splatoon 2 will eat up Arms legs after it has released, but I think it's fair to assume Arms hit 1.5 -
1.7 million before Splatoon 2 came out, considering it had almost an entire month left

for the case of a new console its better to look at percentages, not numbers. the Switch (from most recent data) has sold 4.7 million units. ARMS has sold 1.18 million units. that is an attachment rate of 25% of all Nintendo Switch owners. 1 in 4 people who own a Switch own ARMS.

Now lets shift focus to Sony for a moment. Not too long ago they released a new IP in the form of Horizon: Zero Dawn. It has to date sold just over 3 million units while the PS4 has reportedly pushed 60 million. that is only a 5% attachment rate. as a matter of fact only 2 games released for the PS4 have an attachment rate of 25% or more and those are GTA V and Black Ops 3. and another note - the highest attachment for a game Sony has made is Uncharted 4 with only 15%.

But now in Sony's defense, you cant look at percentages because in that case with Sony's 60 million PS4's you would be expecting every game to hit around 15 million copies which would be ludicrous even consider. At a certain point there comes a shift, and you have to know when to look at percentages and when to look at numbers. these people obviously didnt know.

*ARMS sells over 1 million in two weeks*

Kotaku: This is a sign the ARMS has no legs. It has been out in two different months and only sold 1 million.

Me: The game's sales is only for two weeks.....

Kotaku: Quiet! *Activates trap door*

I agree with axum. This is all quite a big ridiculous.

this!

Attach rate says much more about the game's success. Also for a new IP to reach over a million in two weeks in the fourth month of the system release are impressive numbers rather than anything else..

And Kotaku getting the sales numbers wrong is just bad, I stopped reading that site many years ago.

More booty nintendo. ARMS cannot survive off of twintelle alone

Ugh...Kotaku. There is a reason I avoid that site like the plague.

Apparently, the writer of the article didn't realize that the sales of ARMS were as of June 30, not July 31. Fact check before posting the article, Kotaku.

Yeah, doesn't that figure (1.18m) only includes the last 2 weeks of June? O.o 

Yeeah 2 months is definitly jumping the gun a bit, particularly for a multiplayer focused Nintendo game. I think the game will have decent legs as word of mouth advertising spreads, and nearing thanksgiving/Christmas. It certainly won't hold up in the way I see Splatoon 2 holding up, but it'll still sell respectable numbers for a brand new IP.