The source of that Happy Hour list is pretty outdated, Blackbird has since closed and a few places have changed their hours and specials.
I was at Bao Down last week and they had Kusshi on the buck-a-shuck but they said it was sold out, for the 2nd time lol I wonder if they only stock very low quantities since it is a slightly more expensive oyster.
Ebisu on Robson updated the Happy Hours for a couple years now.
Buck a Shuck in full swing as well as lowered prices on sushi and beer!
3:00pm - 6:00pm - Everyday
9:00pm to 11:00pm - Sunday to Thursday