Yeah i think that was one of the big reasons to release the interlude as a "standalone" episode.The thing everyone forgets about the interlude is that DPC used it to test out the import saves system. If it didn't work he had plenty of time to work things out while starting the rendering for ep 9. I'd much prefer it as it is than ep 9 being released 2 months earlier but with an untested import system which could take months to fix.
But other than that... iam pretty sure, DPC just loves Zoey and write content for her, and wanted to do so a long time now. He even said it himself that it was a welcoming break from the being a DIK story itself and that he enjoyed making the interlude very much and writing for Zoey.
For making the importsystem and testing it, he could have done a very short Episode too... even without MC or any choices... only with side-characters.
for example.. i dont know, a review from the teachers about the midterms and some ridiculous answers just to have a little fun with it.
Like... ah did Dawe really wrote in his mid-term test: "i dont know what 1+1 is, i have a phone for that" He didnt have to write the whole interlude about Zoeys time in San Diego... it could be handled very well in Episode 9 just like the background story the MC tells Bella in the cafeteria... would have been more than enough. But he didnt, cause Zoey is his favorite i think. Well, no ti dont think so... iam sure of it.