Feels like a rebrand of the fully refundable fares or full Y - that being said, the number of terms and options is definitely confusing!
No, they are not full Y, J , W whatever. The Extra fares are just the same as the refundable fare options you see today. You can see their fare basis codes on delta.com after selecting them and look them up on EF. EF shows no magic switchover of fares on Oct 1. The fare filings are the same before and after.