There was no consistent WL construction discount.
If a person booked their WL stay **BEFORE** construction was announced and called Disney once it was announced, SOME such people were given a modest room discount (on the order of about $50 per night) or offered to transfer the reservation to a different resort, possibly without additional cost. What, if anything, people were offered was not consistent. Some were not offered anything (that was our case in 2015, but we were made an offer in 2014... yeah, two years in a row booked before construction announced and stayed during construction...). Guests booking AFTER the construction announcement received nothing as they were notified at booking that the resort would be under construction and what would be affected.
WL has had rooms available in the various normal seasonal room only, package and
free dining offers that there have been, which happened to occur during construction times. But those discounts are not due to the construction.
SW