Are we talking about just butting the wing halfs up to each other with epoxy in between or epoxy/fiberglass? You've heard of fake free checking. Hobbico has invented fake wing joiners. My Hobbico "something" 40 trainer snapped the light-ply wing joiner on a hard landing. POS (piece of ...) plane if you ask me. It didn't seem right but nothing was said about glassing the center in the instructions. I'm at fault too for believing it wasn't required. In hind sight I'm sure no glass is so they can sell it to beginners.

Here's Hobbico's last semester grades...
Marketting: A
Business Management: A
Basic Art: A
Differential Equations: B
Engineering Ethics: F

Back in the day I had an Airtrinics Newera 20. I loved that plane. It finally bit the dust and the fus was trashed. The wing was fine and I decided to see how stong it really was. I put a brick under each end almost at the tip and stood in the middle. It took more than half my weigth to break the wing. Glassed center and no wing joiner. It broke just to one side of the fiberglass.