First: Shimano GRX road/gravel derailleurs and shifters are NOT compatible with the mountain derailleurs (XT, XTR, etc). So an XT shifter will not work with a GRX derailleur.
The GRX and other road bottom brackets are only offered in 68mm and 70mm widths so they will not fit a mountain bike's bottom bracket which is 73mm.
The XT has a 73mm bottom bracket ...
I see no way for the pictured setup to occur while riding.
The silver bushing is bolted or rivetted to the cage plates
Cage plates are contiguous plates of steel with no gaps
Lower jockey wheel is also bolted to chain plates.
These three items form a box through which the chain runs. No amount of folding or flipping the chain would get it out of that box.
I have found that Shimano offers non-series road flatbar shifters such as the 11-spd SL-RS700.
So this one can be used with GRX-derailleurs, as GRX is compatible to all roadbike components Shimano offers.
The original source (in German) is here : https://www.mtb-news.de/forum/t/shimano-grx-schaltwerk-flatbar-schalthebel.908787/
I'd go with XT 11 speed shifter and derailleur. Shimano does not publish MTB-Road groupset cross compatibility and I'd assume GRX and XT are not compatible.
I think a bigger issue is whether a GRX crank is compatible with your bike.
GRX cranks are designed to fit road-like gravel bike frames which may have a narrower bottom bracket than MTB frames. If you ...