Commerce Trigger Auto Update not working?

Summary:

We have a requirement to trigger an "after formula" logic in transaction line.
The triggering point for this logic is when there is an update in line quantity.

_line_bom_item_quantity is mapped to line quantity OOTB.

We have checked the "Trigger Auto Update" feature on this attribute expecting that the logic in our transaction line after formula should trigger on update qty.
However, it is not the case. the after formula logic is not getting triggered.
We tried with a custom attribute to verify if "trigger auto update" feature is working. with a custom attribute it worked the after formula logic is triggered.