He's not trying to convert them
...But how is that consistent with this statement?
"The answer has been here before us all along. An inexorable evolution toward a Vulcan philosophy has already begun. Like the first Vulcans, these people are struggling toward a new enlightenment."
It does seem as if Spock believes that conversion to "Vulcanism", perhaps even Surakism, is the only way to unity. If he's not going to promote that, then what is he doing?
"Evolution toward a Vulcan philosophy" is not precisely the same thing as adopting or being converted to a Vulcan way of life, which I'm not even sure is possible in & of itself, for the whole Romulan race.
I took his statement to mean that they're already doing it naturally without him, & as he believes it's in both race's best interest, he wishes to help them in that discovery. The Vulcan way of life isn't something that is just adopted. As it's been explained, it is something which is attained, & even done so in degrees, such as the Kolinahr
He can't just waltz through there & collect up a bunch of Vulcan hopefuls, like the Pied Piper. He couldn't convert them even if he was trying to. They have to find it in themselves, & his goal is to be there the rest of his days to aid them in that struggle of discovery
It may be that a time will come when they find for themselves a way to exist similarly to Vulcans or even the V'Tosh ka'tur, & suppress their intense emotionalism in whatever way works specifically for them
One would expect that Romulans need not necessarily adopt Vulcan living practices in order to find a new unity with Vulcans. They just need to evolve out of the unsuppressed intensely emotional way of life they've been existing in, or at least that's how it seemed Spock thought of it
That's how I took it anyway. That's why he used the word philosophy. They're not going to have Vulcan living practices, but their philosophies might begin to be more alike. I suppose his statements are subjective though