If its a proof of concept the concept is a "RISCOS Tablet". As STD says there is no point in spending buckets of customers money and their own to provide, on delivery day, a RISCOS Tablet which the customer looks at and says "What's this ? Where's the Start button !" etc etc. Instead the customer can see how a RISCOS tablet would work without anyone spending one red cent on hardware..... Now if the customer is happy with the "concept" then a full RISCOS/ARM version can be built.
As for the ARM is for phone comment, well honestly! Here's a simple question if AMD had the opportunity to provide an x86 chip for phones would it say "No thanks we make chips for desktops not lowly phones" or "Yes please (whilst the dollar signs flash before their eyes)" ? The market is changing rapidly from desktop based computing to hand held computing. That "phone" is slowly turning into an all encompassing PDA and multimedia device. The latest phones have games, MP3 players, PDA stuff and the internet. Everything in fact that the vast majority of people rushed out to buy a PC for a few years back. The x86 family is struggling to meet that demand due to its high power demands. Oh by the way for those obsessed with meaningless MIPS. It's not the MIPS that a phone company worries about its the total power requirement. Since it's the total power consumption that defines the battery life and if you have two chips with the same total power requirement you then choose the one with the higher processing capability, hence why the ARM chip is very popular.