NO NO NO!!! This is a common phrase we hear in Cyprus about weissbiers (AKA White Beers).
A lot of people get confused with the yeast at the bottom of the bottle where experienced barmen and waters gently mix with the remaining beer. The yeast is an essential part of the pour and gives Weissbier its distinct flavor. This does not mean that the beer is fermenting!!!
Do not be confused, I am not saying that bottle conditioning is bad, it is different. Studies have shown that priming and bottle conditioning is a very unique form of fermentation due to the oxygen present in the head space of the bottle. Additional fermentables have been added to the beer to produce the carbonation, and this results in very different ester profiles than those that are normally produced in the main fermentor. In some styles, like Belgian Strong Ale, bottle conditioning and the resultant flavors are the hallmark of the style.
So beers who ferment in the bottles after bottling exist but they are not weissbiers.