A common problem that arises when looking at metrics and analytics of cards that move between Workflows and Boards is confusing and/or incomplete metrics data that affects the accuracy of the analytics module for the given cards.
A common cause for this behavior is when a card has gone through the whole process on a workflow, has reached the Done column, and is then moved to the Requested column on another workflow (or to another board). The card retains all the metrics from the previous workflow (and board) and the time spent in custom columns will be counted towards the main sections of the workflow/board (Backlog/Requested/In Progress/Done/Ready to Archive). This means that metrics from the previous workflow are being attributed to the new workflow/board, even though they were not accumulated there. The initial workflow/board also then lacks the metrics for this card, and it will not be visible on the analytics regarding it.
The analytics of the second workflow will be skewed because the metrics of the card that is currently there were not accumulated on said workflow but on the initial workflow the card was created and was moved through. Regardless of where the time was accumulated, it will be attributed to the workflow and board that the card currently resides in.
For this purpose, instead of moving the card from one workflow/board to another, you can create a 'Card is Moved' business rule which can create a relative card (on another workflow or board) when the first card is moved to Done on the primary workflow/board. This will ensure that each card has its individual life-cycle on the appropriate workflow/board.
Due to the above, frequent changes to the board/workflow's design may lead to such issues in the future, therefore it is recommended that the users take the time to familiarize themselves with the types of workflows and carefully design their board layouts, based on their process and scenarios.