ᐅ Filling drywall joints (on gypsum fiber boards) using joint compound with reinforcing tape

Hello!
I have converted my attic into a living space using timber frame construction. On this, chipboard panels have been screwed on as wall sheathing.
In the bathroom, I have additionally screwed moisture-resistant drywall panels (green) onto the chipboard panels.
Now my question: Do I need to reinforce the existing joints with joint tape before tiling, or is a normal joint filling sufficient? I am concerned that the chipboard and drywall might expand differently, which could cause any cracks to transfer to the tile joints.
I know this is probably not the most optimal wall setup, but I have to live with it for now. How can I prevent movement in the substrate under the tiles yet to be installed? Would using an entire surface mesh be advisable?
Or am I mistaken, and are my concerns unfounded? Of course, I would prefer to fill the joints without tape to reduce effort, but only if there is no risk involved.
Thanks 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 would require significantly less effort without it, since you have to apply joint compound anyway... Structurally, it shouldn’t be a problem, as long as you’re not planning to tile directly onto the particle boards.