That's the one. TP Dihederal is not a stability thing in most airliners.
Our two Welsh and Two Chinese friends who are responsible for lateral stability (Di Hedral, Sweep Baack, Hi Fin and Hi Wing [you will remember that now - huh? - lol]) have more than enough effect on the mainplane and fuselage. You do get some Lateral Stability from DH on the tailplane - but usually you are looking at a cleaner airpath solution on the approach...
MG