Your ears are designed to be optimised for front facing stereo localisation.
The further the sound source moves towards the rear of your head the less resolution can be defined, so it becomes less important to match the rears with the fronts as you'll notice the tonal differences less.
Side pairs are possibly more debatable. I've chosen to match my side pair with my fronts, so my LCR and side pairs are all Arendals. My rears are currently KEF T101s.
Edit: to specifically answer your initial question, yep you should be fine with that setup!
I have KEF R Series all round simply because that's how my upgrading progressed. On the very few soundtracks where the sound pans right around the soundstage it sounds very good. The conversations at the beginning of The Revenant pan perfectly. It certainly isn't a rule that is set in stone and a lot of people go for the surrounds that suit their room more than the timbre and there is nothing wrong in that.