Not really. The Twitter API allows both read-only and read/write access. iOS, as a system-wide grant, has read/write permissions - but apparently does not allow users to specify per-app permissions to be that granular.
Moreover, the app was apparently locking out paid users from any access at all unless permissions were granted, which in itself shouldn't have made it through Apple's vetting process in the first place (exception: twitter clients). The majority of apps will only need access to the "share sheet" for posting to twitter, which AFAIK doesn't require explicit permissions (similar to sending an email; the user must hit send)
I don't know since I don't use the app; from the description given in the blog post it seems highly doubtful that the app specifically told him it was going to post to his Twitter account on his behalf without telling him.
Also the app appears to be in violation of the iOS guidelines (see another post upthread), which means that it is not generally understood that apps can post on your behalf without telling you just because you give them access to your Twitter account.
