I would tape both sides. While I doubt that the tape is structural (if so someone has got some explaining to do...) it really is there to keep the panels in position and straight.

It is theoretically possilbe that you could epoxy only one side, but that would have to be the outside of the panels.

It will save you time in the long run to glue both sides now, even if you expect to sand these off when the hull is stiched together. Imagine the time it would take to unstich a panel and re-epoxy and restich if one of the butt joints failed when tightening all of these together.