That's not exactly true. The attack can be performed against WPA not WPA2. To be more concrete against TKIP. But the attack can be only done under very special circumstances and is not conclusive. I found an amazing source about this. Is in spanish so I tried to translate it doing my best.
TKIP system is using RC4 protocol, the same as WEP with two ...
TKIP is deprecated since 2010, and practical attacks exists against it. You should not use it. Since you do not have devices that requires it, you have no reason to leave it activated and all the reasons to disable it. I suggest you look into your range extender manual for how to configure it.
Some historical perspective should help to shed some light on the confusion. The gist is that "backward compatibility" is the reason we still see TKIP around.
802.11-based WLANs originally came only with WEP, which was soon discovered to be too easily cracked to be sufficient for general usage in WLANs.
IEEE started working on 802.11i, an amendment to add ...
There is indeed a lot of unclear information out there. Your first idea was correct, to the best of my knowledge. While I can't seem to find an authoritative source right now, this DD-WRT wiki page explains it the way I understand it:
TKIP vs AES-based CCMP
Defines the algorithm used for message integrity and confidentiality.
WPA was designed to ...