Except that it means I have to look for a desktop computer to be able to see what the site was all about, not even switching mobile chrome into desktop mode helped to see what it was all about.

Given the amount of people whose main device is a tablet/mobile, a bit more of attention would be welcomed on a Website which is supposed to promote the Web design capabilities of the authors.

You didn't notice the behavior of the site. It doesn't allow you to browse it from a mobile device, not even when requesting desktop version. Perhaps faking agent would work, but I wouldn't be surprised if you'd have to spoof resolution/window size as well.

I got the message on my desktop. Because my monitor is configured portrait, not landscape.

When I stretched the browser into a second monitor, it came to life.

So it's the browser window dimensions, apparently. But it was still unnecessarily restrictive.