I have been giving more thought to the Romulan question (which is inexorably linked to any discussion of Vulcan history) and believe that another possibility can reconcile the two, one which fits in well with established Trek lore (in style, at least).
We have to accept that there is a biological component to this. After all, Romulan traits were obviously inherent enough to show up as distinct on 23rd/24th century medical scans. In other words, despite the relationship, they were obviously regarded as another race (maybe subspecies?) by the Federation, and not just another faction of Vulcans.
Maybe it's more in line with Andorian/Aenar than European/African. Maybe the Romulans' ancestors were already what they've been seen as or well on the path to becoming this by the time they left Vulcan. Obviously the Aenar had millenia, if not millions of years to diverge, but who's to say it wasn't the same on Vulcan? It's been less than 50,000 years since another species of sapient humans walked our own Earth, after all (even if we rarely crossed paths).
It's certainly not outside the realm of possibility that the Romulans were already "Romulan", in form if not in name, long before they left Vulcan. Hell, it's established that even the Vulcans' own recollection of that time and how the Romulans fit in is fragmentary at best. History is funny like that (remember the "myth" about Troy?).
So what this all means is that maybe the Romulans tell us nothing at all about the Vulcans desire/need to suppress their emotions.