He can play both sides... he's been playing left because Tupouniua was right side dominant and Crichton has flexibility to go both sides. Pretty sure Crichton played his whole Bunnies career on the right edge.
Dave also came through the grades as a right side second rower... and dominates over there due to his right arm offload.
He was mostly playing right for Broncos because Glenn was left side dominant... but he got shifted to the left for a period, probably when Glenn got injured, and had some success.
The next year when he went to the titans he started on the right edge (Beau Fermor has been left side 2nd rower up until this year), but their attack was useless and couldn't really get him the ball so they moved him to the left and he had some success... probably when Beau did his ACL.
He then started left side last year and had Foran feeding him the ball.
I think his game is best suited to the right edge with his right arm carry, step, offloading, etc. and I could see Robbo shifting him to that side.
Either way both of them can play both sides so there isnt an issue with playing them both in the starting side