Firstly I don't think they get the bonus in the xp weekend.
When you make a wine it won't ferment for around 10-15 seconds. Every time you make another wine the clock resets. So if your quick banking you will not get an xp drop. So basically you can do like 1000 wines without leaving a gap over 15 seconds between each wine and when you stop and wait 15 seconds finally you will get a 200k xp drop at once.
What people are suggesting is that you do like 5k wines before bonus xp starts then log out. Log in and wait for the xp drop which would be 1m xp but in the bonus would be 2.7m xp. Although again I don't think they work in bonus xp