Every limiter in my collection claims "true peak" detection. None of them do it without some small degree of error. None of them exempt you from the need to leave an appropriate amount of headroom to avoid intersample overs. Most significant, none of them can guarantee that you won't get clipping after MP3 encoding.
Consequently, it's still best practice to leave adequate headroom regardless of what limiter you use - which makes any vendor's claims of superior ISP detection moot.
Now, Ozone does have this cool AAC/MP3 preview feature. What I haven't been able to determine is whether the peak meter can reveal encoder ringing when this feature is engaged. So far I haven't seen any differences in the maximum-peak display when the encoder preview is active, which leads me to suspect the peak meter isn't useful for this. If that's the case, it's a missed opportunity for iZotope. I hope I'm wrong. Anybody tested this?