Adjustment Entries in ILE

G/L is affected because you have expected cost posting turned on in the inventory setup, which means not only invoices will book inventory costs but also shipment notes. In my experience most companies will either not want it or if yes then link it with some very "technical" G/L accounts that are not part of the usual balance sheet and P/L.

Another thing is that you can only do an undo as long as it is not invoiced, and you are closing financial periods without invoicing shipments? That... cannot be a correct closer procedure. Seriously one of the most basic steps of closing is to ensure all shipments are invoiced.