"mirror" column cannot be mirrored

Link to the same board to retrieve different rows information, ends up stuck with this error message. is this a bug or the feature is not ready ?

looking at the below method, it seems like this can be done when 2021 , but now this is not allow anymore ?

https://community.monday.com/t/calculating-the-days-between-dates-from-different-items/18330

Yep, I was just trying to get a subitem rollup column to mirror on another board, but it’s blank. Presumably because a rollup is technically a mirror of the subitems?

This change was made last year at some point to not allow connecting to the same items within the same board. I believe this caused circular references in some cases.

Thanks,
Mark