It’s possible that this feature is slowly being deprecated for new accounts, so I do apologize if you are no longer seeing this option when utilizing the updates section.
While it’s not possible to mirror the updates section of an item, I would suggest utilizing a text column and mirroring that between the boards if possible. Otherwise, you will need to continue going to the original board in order to see that item’s update information.
However, I have passed along the feedback for you but you can also vote for and support this feedback post that our Product Team also takes into consideration when making plans for future adjustments to the platform: Feature Feedback Post
I hope this helps!
Cheers,
Jenna