It’s been a few years since I’ve been in an Apple Store, but they also tend to show all colours (in contrast to other retailers that might have one of each model.) So it would be expected that they have (at minimum) the 4 iPad colours, an 11” Pro in one colour and a 13” Pro in the other (one with Nano texture), a Mini, 11” Air and 13” Air showing 3 of 4 shared Mini/Air colours and one other with the 4th. If they were trying to save space/money then you could argue that people wouldn’t need to see it to know what they were getting with a Silver base iPad or Space Grey Air/Mini, or would opt for them if they had decided on the right model for their needs but didn’t like any of the brighter colours on display.
They won’t have any models that aren’t current on display, so the only thing you can do there is order a Certified Refurb and return it if you aren’t happy with it.