That only works for multiple pack lines lines on the same packer (and from the same source order).
If part XYZ was on Orders 1234 and 1256, it could be shipped on the same packer if “Combine Pack Slips” is enabled. But regardless of the “Consolidate Shipment Lines” setting, the Get Shipments during Invoice entry, would create two separate invoice lines.
If Order 1234 had two release for XYZ, and they shipped on two separate packers, that too would create two separate invoice lines.
It seems that “Consolidate Shipment Lines” is only for taking 10 Pack lines of the same Packer, from the same Order, and making a single invoice line.