It's all about trickling features to maximize profit. And Apple is not new at this.Has nothing to do with greed
You know how many parts which would be needed to supply both models? A lot.
Good luck finding any smart phone camera with periscope lens on a phone as small as 6.1
As for parts, Apple purchased parts in advance. Apple would've had deals and contracts with parts manufacturers for 2023 iPhones by now as they would already have projections how many iPhone 15 they want to make. This is why Tim Cook is paid the big bucks. Apple's greed = record breaking revenues = happy shareholders.