MP, best hand South, Instant, Pro GIB v 30.
The system opening bid with 4-4 in the minors is 1D
In that context, 3D by North seems wrong to me.
GIB is not slow to believe opponents' bidding. They have bid and supported Spades, and North has two of them. It seems rather unlikely that South has 4-3-3-3 shape with 4 Spades, being the only shape where the combined trump length in Diamonds will be more than in Clubs.
On the other hand, South could well make a support double of 1S with 3 Hearts and 5 Clubs. Sure, in that case he may (but may not) have 4 Diamonds. But if he has 4 Diamonds he will have 5 Clubs, and if he has 5 Clubs he need not have 4 Diamonds.
Furthermore, North knows that we have only a 7 card fit in Hearts. The double of 1S I understand shows 3 Hearts +/- zero.
Playing with a human partner I would double 2S for takeout with North, but perhaps GIB plays it as business.
2N may be a risk too far. But if not passing, doubling or 2N I far prefer 3C by North over 3D.
Not that it would help us a lot on this hand.