Question about new Airport Base Station's speed with G Devices

I got this quote from the Apple web site:

Based on a comparison with Apple's 802.11g products. Comparison assumes AirPort Extreme network with 802.11n-enabled computer. Speed and range will be less if an 802.11a/b/g product joins the network. Accessing the wireless network requires an AirPort or AirPort Extreme enabled computer or other Wi-Fi Certified 802.11a/b/g-enabled computer. Actual performance will vary based on range, connection rate, site conditions, size of network, and other factors. Range will vary with site conditions.

Now I understand if you put a g device on this network the g device will run with g range and speeds. The way it's worded I almost get the feeling that having a g device on the network will slow the speed of the entire network down including n devices. Is that true?