campboy, on 2013-November-18, 20:10, said:
It's not obvious to me what is suggested by the UI. The fact that partner is weak might suggest bidding, but the fact that we are unlikely to have a fit (assuming he was thinking of pre-empting in a minor) might suggest passing.
The fact that partner is planning to preempt makes it a good time to psyche, we will not be buried by partner say bidding slam with a 19 count, and they might well have a game if partner has a preemptive hand in which case opening will make it much harder for them to bid it. They certainly make a partscore in something if partner has a preempt so even if we drift off a few NV it won't be bad. The UI certainly makes opening the south hand much more attractive and profitable, lower risk and higher reward.
It is the same reason one might open this hand in 3rd seat, it is a tactical bid that has much lower downside when partner is known to not have an opening bid. Being able to pretend like we are third seat and bid accordingly because we know partner has a weak hand seems like utilizing UI.
Let's put it this way, let's say north had said out loud "I have a weak hand that I will open 2D or 3m or 2/3M" and south opened 1S with a horrible 9 count non vul. You would rule no foul? That is effectively what happened.