As per sir firewired's previous posts (if I remember it correctly) the R3 and R1 use the same master for DVDs. The R1 has no problem displaying it's being THX certified because they paid royalty to THX or something to that effect.
The R3 on the otherhand, though it used the same master, don't display "THX Certified" and has no THX Optimizer due to region limitation of the certification. And maybe to lower the cost of the R3 releases.