How much of that volume was the stabilizer?
My understanding of the HB stabilizer is weak, but it looks like it isn't converting HBD to HIVE.
As I understand the primary purpose of the HBD stabilizer is buy HIVE when the price of HBD is over $1 ... which doesn't happen all that often.
This is the ausbit page on the HD Stabilizer and this is the HiveBlocks page. Most of the transactions are back to hive.fund but there are some HBD convert requests.
Stabiliser works both ways.