>>26787811100% this.
The parallel universe bullcrap spewed in Delta Episode was simply superfluous and was only brought up to justify mega evolution in ORAS.
Of course, it's superfluous because the presence of mega evolution is of relatively little importance from a narrative perspective and neither the children nor adults give a rat's ass about why or how the mechanic is present in a remake title. And unless gamefreak has a marked shift in their attitude to narrative, the status and order of the franchise 'timeline' is essentially irrelevant and will not be brought up again in future titles regardless. It's unlikely we'll be seeing another 'red gyarados' multiverse anchor.