I've seen people using this technique multiple times where I work.
Say I have an element:
<div class="new tile">I'm a new tile!</div>
I want to set the color of this tile as red, so I do so:
.tile { background-color: red; }
It works fine for a couple of months. But then someone else writes a new rule to set color below this one:
div.new { background-color: blue; }
The old rule had a specificity of 0 1 0 and this one has 0 1 1, so the color is changed.
His code is none of my business, but I don't like my tile set to blue, so I "force" it to red:
.tile.tile.tile.tile { background-color: red; }
This new rule has a higher specificity of 0 4 0, so it does set the color of the tile to red.
Is this intentional? It looks like a terrible practice - right up there with (mis)using !important, because this is basically referencing the same class. IMO, they could just patch this in some future CSS revision to only consider one class/element/id once per selector.
Fiddle if you want: https://jsfiddle.net/x634zh7u/
Edit: I see this question is closed as opinion based. What I mean is, does the CSS standard mention this anywhere as to why using the same class multiple times works?