Why not build it on older, unused hardware, then. It's not going to help to have to go through all the trouble of getting something going on ARM only to have to start over on x86, for example.
The audience for Pi are youngsters who want to play. They don't have an office full of legacy x86, PPC, Mips hardware to play around with.
A tutorial like this is a great place for a youngster to start playing around.