It might be an intentional synonym usage of inputs and outputs, I don't know if he ever used inpoints and outpoints as input and output but both the word had been used by Gavin Anderson prior to this post. satoshi posted this on August 10 while Gavin Anderson referred to input and output of transaction in July 18. So, it's pretty sure it didn't change to input and output, I mean there was no transition of the terms. More like, satoshi used to refer as like this.
satoshi first used the term input and output in July 25, 2010 but that doesn't look like he was talking about input and output of a transaction, it was about some program.
Just adding, theymos used the term input and output at October 20, 2010.

TL;DR- This has nothing to prove. I would say satoshi used to say inpoints and outpoints while others used inputs and outputs.