you used to have to send three (or more) screenshots... one for each of the sectors showing available, and a third for the end-to-end showing not available. So a booking MEL-NRT would require screenshots showing MEL-BKK available, BKK-NRT available, but a third showing MEL-NRT not available.
This new workaround seems to suggest the first two screenshots are not required.
One big benefit for this would be LH F. It is often wide open at T-14, but LM would only offer select days. You couldn't write to them and ask you to book it without a screenshot showing it was available. Now... perhaps not required and it can be booked.