I missed a decent slam on the 1st board of this set from yesterday:

All white, IMPs

2nd seat:

Q82 / JT984 / - / AQT83

4th seat:

AJT / AQ75 / QT63 / K2

Auction:

P - P - P - 1N
P - 2D - X - 3H(no agreement)
P - 4C - P - 4H
P - P - P

After the hand 4th seat commented that 2nd seat should have cuebid 4D, instead of bidding 4C.  4th seat responded that diamond shortness was implied by the initiation of a slam try as a passed hand opposite a 1NT opener.

Assign blame and/or discuss the relative merits of the arguments made.