What’s incorrect about this? Nepal’s flag is indeed the only non-quadrilateral flag of a sovereign nation, shaped like two pennants.
Every rectangular flag has a specific aspect ratio and it's incorrect to make it wider or narrower than that. The Swiss flag isn't special just because that ratio is 1:1.
I went to a church that called a "rectangle" a "square". It drove me nuts.
For context, after the first round of singing, someone would announce "kids go to children lessons, light up by the door with the green square (it was a rectangle)". They did this every service.