Shimano GRX and cross compatibility

One more option might be the tiagra 4700 10 speed 48/34 crank or even just the chainring if you can find it

Does anyone know this to be true? I thought the outer ring on GRX was still mounted to the inside, of the arm, and ultegra was on the outside.

I really want to be able to run 46/36 (or 38) or a GRX crankset.