Link between mrp_full_pegging and mrp_onhand_quantities

In mrp_full_pegging, there is a transaction_id which the TRM lists as a foreign key to mrp_recommendations but does not mention a link to mrp_onhand_quantities.  There is a transaction_id in mrp_onhand_quantities which links accurately to mrp_full pegging most of the time to get down to the subinventory level for onhand inventory.   I'd like to know if using the transaction_id to join mrp_full_pegging to mrp_onhand_quantities is standard supported functionality.

The issue I'm seeing is that sometimes, when we have the same item, project, and task in two different subinventories - one that's nettable and one that's not, the transaction_id in mrp_full_pegging matches the transaction_id in mrp_onhand_quantities for the non-nettable subinventory.  And the transaction_id in mrp_onhand_quantities for the nettable subinventory is not in mrp_full_pegging at all.