Yruth 8k is correct as it is an 8k resolution at an aspect ratio of 32:9.
Now a proper & accurate description would be.
8k half height. With a pic showing 4k at 16:9, 8k at 32:9 & 8k at 16:9.
8k is different at different aspect ratios the real misnomer is presuming & not educating readers on understanding how aspect ratios & resolutions affect one another.
So 2160p at 32:9 is 8k half height.
With that being said we can't blame media for being influenced by the public that was only thinking that 8k only can be represented by 16:9 (the standard aspect ratio used today for TV).
Or the fact only qhd is accurate to call 2.5k as the vertical number is minimally 2500. 4k is actually 3.8k & doubling it would be 7.6k not in reality 8k as its almost 1/2 k less.