Choosing Hidden Power Rock on Android gives 30 IVs in HP, Attack, Special Defense and Speed, resulting in Hidden Power Ghost actually being put on the Pokémon. It should give you a 30 IV in Defense, Special Defense and Speed. Thanks to user Oggy for reporting this to me on the server. I have confirmed this bug myself, and compared it with the Windows client.
30 30 31 31 30 30 is HP rock. 31 30 31 31 30 31 is HP ghost. This is what the desktop client gives Did you try to put it on an IV restricted pokemon?
I think Oak made a minor mistake, because 30 IVs in HP, Attack, Special Defense and Speed actually is a Hidden Power Rock, but I still think that the Hidden Power selection is bugged on Android because if I recall correctly, someone on the server that the Hidden Power type he selected wasn't the same one as he battled on Android. I can't test it myself, because my phone broke, so someone else with the Android client should test it again (just to be sure).
The same equation that decides the values in teambuilder is the same that decides the color/type in battle. The server can give you different IVs when you log on because it finds them to be illegal. Like a Xerneas with 30 30 31 31 30 30 (HP rock) becomes 30 30 31 31 30 31 (HP ghost) because it must have 3 perfect IVs to be legal.
Sorry for the delay in response to this. The listed IV combination is only the default for HP Rock on the desktop client. One of the alternatives is... 31 31 30 31 30 30 ...which ultimately fulfils the 3 perfect IV requirement for the Xerneas I was reporting it from. I believe the best way to make HP Rock Xerneas possible would be to change HP Rock's default IV spread to the one I suggested above, as this will prevent any future issues with restricted IV Pokémon on either version. But yes, it was getting HP Ghost on the server instead as its Speed IV was being forced back to 31. There was no notification of this happening on Android though, as opposed to the Windows client, which states that Xerneas cannot have that specific Hidden Power, or must have 3 31 IVs. The Windows client also allows HP Rock on Xerneas through the IV spread I posted above, and does not display any of the other options.