It make sense since newly created accounts are able to post only 3 comments (2 on my tests) for their whole mana. That means they have to wait 2-3 days to edit it or comment under it. A free start without these limitations could be helpful for them to get used to the system and interact freely. Then they can decide to create a steem account and invest in.
My only concern, oauth is not enough to avoid scam attempts. So far we've blacklisted many accounts for using multi-accounts which all had multiple google accounts.
I did not question whether Steem auth should be preferred or not but that it is not included among others means to log in. But I can understand it as Steem does not hold any personal data and thus making it significantly different than signing in with other accounts.
I agree that the decision is good for people who don't know Steem and may decide later whether they want to join. Though, if Steem is not required and people may use the platform without a Steem account, they may miss the potential of the blockchain and may not join other apps. But those thoughts are out of Utopian scope.