No. It doesn't. Where are you getting this from? Again, if a thin piece of vinyl blocks reception, what would a thicker rubber/plastic case do? Common sense should dictate this, but apparently you think otherwise.
The reception issue has to do with your fingers (or another conductive material) touching the antenna thereby bridging two of the antennas. A great article/demonstration can be found here if you want to read more: http://www.anandtech.com/show/3794/the-iphone-4-review/2
The reception issue has to do with your fingers (or another conductive material) touching the antenna thereby bridging two of the antennas. A great article/demonstration can be found here if you want to read more: http://www.anandtech.com/show/3794/the-iphone-4-review/2
...It still covers the antenna and it does still block the reception, a little bit but does...