Sorry, should have posted yesterday morning that it had gone up to match BA to the penny.
As well as getting the money from reward bookings, if you change your date and the ticket has to be re-issued instead of re-validated then they can charge the increased YQ tax.
This is normally when the class you originally booked in is not available so you have to pay to make the change, upgrade the ticket AND the increased tax.
It sneaks some more money into their pockets in a few little ways but I still find it a sneaky little trick.
Move to the red side...