I see 3 limitations but maybe I'm missing something:
1) If you use "Incoming Document" (or any other feature allowing to directly retrieve the draft supplier invoice - header and lines - in your Business Central database) then the purchase lines are arleady filled in and therefore I don't see the interest of clicking on "Get Receipt Lines" it would just overwrite the purchase lines that have just been imported.
2) Second issue is that you assume the receipts and invoicing are done at 2 different moments. But in many cases, it is managed simultaneously and users don't want to manually receipt mutliple POs just to be able to do "Get Receipt Lines" after that. So basically there should a function from the draft purchase invoice allowing you to match this invoice with the PO and when you post that it automatically books the receipt, the invoice and update the PO accordingly.
3) Last point is very similar to point 2, but what if we are talking about subcontracting invoices or non-inventory items? In this case, you just don't care about the receipt (from a user perspective). But maybe this last point is again another missing feature because basically in BC everything revolves around quantities. Therefor, there is no OOB feature allowing you to manage a purchase order with 1 line and 1 whole amount and after to book multiple purchase invoices which are progressively matched to this PO until the whole amount has been invoiced (it can be managed sometimes by tricking the quantity field but definitively not user friendly).
