As for the lack of see through case back, this is indeed very easily understable.
First, it would augment the thickness of the watch, which was the main critic on the XGT case.
Then, it would not be faithful to the spirit of the original Reverso 1931.
So, I think that it is a great move.
Yes, the XGT case is smaller than the Grande 976: 2mm x 0, 75 mm less.
The respective thickness of theses watches is important, too: 7, 2 mm for the TT 1931, 12 mm for the XGT, and 9, 7 mm for the Grande 976.
AFAIK, this is a LE of 1931 pieces, so if you want one, you will get one.
Now what do I think?
I'm very enthusiast on these LEs ( I didn't see, yet, the non LE version ).
I want to see it in the flesh, and have a precise idea on the dial.
So, I will come back to this watch, for sure, and will give you my definitive thoughts on it, but a very positive " a priori ".
Best,
Nicolas