Brant, some quick cave man calculations. I know the configuration isn't exactly as the premise but it gives an idea.
I am going to use Joel's numbers to build on rather than research this myself.

The 7D II with 336 sq mm and 60119 pixels per sq mm.
Square root of 60119 gives us 245.19 lines per mm.
Multiply that by 2 gives the linear distance between pixels over the sq mm, 490.38 mm.

The 1D x with 864 sq mm and 20949 pixels per sq mm.
Square roof of 20949 gives us 144.73 lines per mm.
Multiply that by 2 gives the linear distance between pixels over the sq mm, 289.47 mm.

490.38 / 289.47 = 1.69 more linear separation of pixels with the 7D II.

Maybe it plays a part?