I'd hope "show cases for android phones on an android phone" to be something rockstar engineers at ad companies figure out rather easily.

Or the ad content isn't being made specific enough. I know that at least for the cheap Aliexpress tier stuff, they'll make the same basic design for 12 different phones, so theoretically the same product listing might include iPhone and various Android variants, but the description might fail to reveal that.

I'm sort of surprised that the industry isn't 70% print-on-demand these days-- just say "we have a nice sturdy case design for the top 500 phone models, and upload your own art".