Tile Sampler on Mac and PC give different results

On a PC, create a standard gradient linear 1 node and feed it into the input of a tile sampler. Set it up so you can see the tiles without any additional rotation. The patterns you see in the tile sampler should all be the same orientation as the original input. White top, black bottom.

So when viewed on a PC the tiles appear the correct way up.

But share that material to a Mac and they're flipped vertically or rotated 180 degrees.

So either -- the tile sampler is flipping the tiles or the default linear gradient on Mac is vertically flipped. I've not got access to a Mac and the artist I'm working with can't use designer.