Filling drywall joints (on chipboard) with reinforcing tape

Hello! I have converted my attic into a timber frame structure. On these, chipboards are screwed on as wall paneling. In the bathroom, I have additionally screwed drywall boards (green) onto the chipboards. Now my question: Do I have to fill the existing joints with joint tape for reinforcement before tiling, or is a normal filling of the joints sufficient? My thought is that the chipboards and drywall boards expand differently and thus any possible cracks could transfer to the tile joints? I know this is certainly not an ideal wall construction, but I have to live with it now. How do I prevent movement of the substrate under the tiles to be installed, maybe a full-surface mesh?? Or am I wrong, or are my thoughts unfounded? From the effort point of view, I would of course prefer to fill without tape, but only without risk. Thank you for your helpful feedback. Best regards ratzec

You mean only the joints of the drywall panels, right? I would use joint tape or reinforcing mesh. I don't understand why it should be noticeably less effort without it, because you have to plaster anyway... In terms of construction, it should not be a problem as long as you don't want to tile directly on the chipboard.