it's a feature if the developer's intention was to enable that advantage the way it was used, but since within a day or two they >FIXED< it after raising awareness, I think it's fair to say it was a BUG (I'm not shouting or angry, I'm just using capital to emphasize the pivotal point imho).
so theoretically, if you find a spot on a map, where you can see through the wall because of a texture glitch, does that give you an advantage? yes it does. could anybody else find it? yes, sure. is it an intentional feature of the game? absolutely not.
there is a lot of money on the table, obviously everyone tries to be ahead of everyone else, but in a professional environment it's quite unethical to exploit an issue with the game itself, in my opinion it's just simply matter of fair play; it can't and shouldn't be punished by any means. kudos to astralis they've found something no one else was aware of for months and months, clearly they put in the time and effort to master the game.
1Naeqo: it was a response on TACOs tweet saying that he knew about for a month, sorry, but I won't put effort into finding it :D