Thanks for your inquiry. Once available, updates are released to Carriers and thereafter, it is at the Carriers discretion to release the update to customers. Since updates are released by Carriers in waves, we’re unable to determine when your device will receive an update. We appreciate your loyalty.
I have an unlocked s9+ (SM-G9650) and received yesterday only the july security patch without the one ui 2.1 update. So it seems that the information you provided it's not very correct.