Restrict Billing Block in Sales order

I have a question. We can apply Billing blocks on Header and Item level in a sales order 'OR' document.

we  blocked an User from removing Billing block  for Object V_VBAK_ATT ACTVT 43 on a Sales order for both Header and item level.

She gets 'Authorization block' when she double click on item --> Billing documents--> and remove billing block (Field VBAP-FAKSP)

But, Issue is, on the Sales overview screen of the sales order, she scrolls towards the right of the item and removes Billing block on Item. This time she's able to save the document and NO authorization block message.

I checked , both are same field, as it should be, VBAP-VAKSP.

Can you please advise?