What would be the problem if he were Satoshi Nakamoto? He'd rather deserve the Nobel prize.
From the article:
"Guardian Australia understands the raids are not related to the claims that Wright may have been involved in the creation of bitcoin, but are related to an Australian Tax Office investigation."
I don't know if there are other crimes for which they intend to charge him, but that's the first one that pops to mind.
Also, they've obviously had meetings in advance of "what do we do if we determine the identity of Satoshi", because this raid was FAST.