I think the only issue is I would make sure you buy a high quality one, since that will be exposed to more moisture than if it were outside the shower itself and a cheap one might pit/rust faster. Or at least make sure that you keep some extra wall tiles on hand if you ever have to swap it out and need to change the mounting holes. Make sure it can be mounted securely - either add blocking in the wall if studs aren't spaced right or use wall anchors.

And last it might be nice to see it in person and do a fit test of your bottles. As product sizes have gotten smaller, they've also gotten skinnier and would be annoying to have it falling through the cracks all the time.