You will always see videos of channels you are subscribed to in the subs feed. We added the bell a while back for proactive notifications which not all viewers wanted to receive. The bell gives viewers a choice. More here: http://goo.gl/XLDtz4
Didn't you say in the video yourself that you only push updates based on the user activity and the only 100% way to receive notifications/updates on your subscriptions is the bell? So far it doesn't look like some vids didn't show up but I almost missed some because of the delay.