I think someone might be projecting here.
I fit your description of the experienced diver above and I can't even begin to imagine what you mean by needing to "throttle back" if I was paired with a newly certified diver.(Other than the likely scenario that the new diver will go through gas faster than I will.) Further, I can't imagine saying or doing anything that would make that newly certified diver anxious or in anyway convey that their presence was "impeding" my dive experience... largely because it wouldn't.
If there is any merit to your contention that such a buddy pair is "unsafe" due to "stressors" much of the blame for that needs to be laid squarely at the feet of the more experienced diver. Perhaps they forgot that they were new divers once? Or maybe they were born as an instructor with 1,000-2,499 logged dives? Or they are just the type that stamp their feet and piss and moan to everyone within ear-shot about every perceived slight, including the egregious affront to their full-throttle dive style that a less-experienced dive buddy might present.
It's interesting to note that all the really good solo divers I know tend to make really good, considerate dive buddies. However, all the divers that I know that make really poor, inconsiderate buddies... seem to end up doing most of their diving [-]solo[/-] by themselves.
Funny how that works out, huh?