Tobias Palm commented directly to assuage people of their fears that the platinum trophy for Life is Strange: Before the Storm would only be available to Deluxe Edition owners.
Official Community Manager for Life is Strange and self-professed platinum hunter here. :)
This was a mistake on our side and it is not our intention to gate the Platinum trophy via the optional Bonus Episode in the deluxe sku. We've already started speaking to the first parties about rectifying this."