Can someone explain what members are doing to make availability show the way it does?

[dismedvc]

For example, BLT standard view would likely show a lot of those open days already gone

You are correct, now that the booking window is so close to NYE.
The same pattern was showing up a few days ago for BLT standard view 2BR's, both lock off and dedicated, where only the current day was unavailable. However today, the BLT standard view 2BR lock off shows Dec 29 through Dec 31 unavailable and the BLT 2BR standard view shows Dec 30 through January 1st unavailable,

ETA: BWV 2BR standard view are still showing only the current day unavailable with the 7 days before and the 7 days after available.

 

[dismedvc]

Computer walkers.

That has to be it. When someone modifies a reservation to drop a day at the front end and add a day at the back end, the "old" reservation stays in place until the modification is complete. Completing that modification involves clicking through several screens and I do not think anyone could manually complete the modification process fast enough for the previous day (which had shown as unavailable prior to 8:00 am) to show as available at approximately 5 seconds after 8:00 am.

That does not mean that most walkers are computer walkers, but it would only take one Computer walker to drop that prior day for it to show as available.