Is this true ? (about IE 7 and cache)

I stumbled on this statement in Wikipedia :

So if I clear the cache (a setting in IE 7) the index.dat file is overwritten.
Is my guess that this is not true or only partially true correct ? I thought it wasn't that easy.

 

gone are the days of toil with the utils able to delete index.dat (some even allowed a peek inside), gone are the days of .bat files deleteing IE temp folders on reboot. Now all of that on a press of button

 

I've had IE-6, 7, and currently 8 (and Firefox, my default) set to clear their caches when exiting. Can't remember for sure about IE7, even though 8's not that old, but if I opened Disk Cleanup after closing IE6, I found that quite often a fair bit had been left behind which I then cleared with DC.