It's a bit of a gable, overclocking. Sometimes you have average results, other times you're in luck. The ASUS 6800 XT LC review for example shows that we can hit 2700 MHz on that GPU clock. But the bar is set even higher for the 6900 XT. 

It seems that the 6800 XT has a hard target cap at 2800 MHz, but the 6900 XT can be clock (and I am not stating stable here) towards 3 GHz.. perhaps when using sub-zero cooling one can achieve such numbers.

Patrick Schur on Twitter reports all this. Schur states the RX 6900 XT has a raised engine clocked limit of 3.00 GHz. So that's a 200 MHz increase. Combine that with 512 extra shader units, and we're sure Fire Strike records will be shattered. Keep in mind, you'll achieve such values only in highly overclocked and cooled conditions, if at all.  

AMD Radeon RX 6900 XT = capable of going for a 3 GHz OC?