I think 3♦-3♥-3♠ - three bids are competive,the goals are to look for a best spot as a final contract,so 3♠ should show they can't look fot best spot,and should be sign off.
It is weak showing instead of twice rebiddable ♠ as strong showing.
3♠ led to Gib E's choice of 4♠ wrongly,
So 3♠ as a twice rebiddable ♠ - strong showing,it is a impossibe descriptive bid.

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