gnasher, on 2012-October-22, 02:01, said:
The problem is that you know (from the UI) that partner will jump to 6♦ if you do that. He (or she, I have no idea who the opponents were) was clearly considering cueing for diamonds, or bidding 4♦, last time. In my view, that is not carefully avoiding taking any advantage from the UI. 4♥ is also a puppet to 6♦ in this partnership's methods of using a slow 3NT instead of a serious or non-serious 3NT to express doubt.