If you were using an alias nobody seeking Satoshi Nakamoto would ever find that track. But in case your name can be connected to Satoshi Nakamoto on-line and you want to avoid that, it makes sense posting something that is not consistent you being Satoshi Nakamoto. Then any casual researcher will eliminate you as a potential 'suspect'.

As some others have noted, Satoshi probably didn't understand how big Bitcoin would eventually evolve, and it was only later that he wanted to cover his tracks.