This may come in a later video. I noticed on youtube a comment mentioned that this seemed more of an elaboration of why to not gank a losing lane, instead of a manner in which to help/manage those lanes.
This takes a few things to line up but a lane that is behind can be ganked. The points you mentioned need to be understood. Can your lane help fight? How far behind are they? Among other factors. However, one of the biggest fears when ganking a losing lane is the counter gank. If your lane is losing 1v1, you need to know if you can win 1v1 or 2v1. Generally if a lane isn't too far behind you can win 2v1 pretty easily, however if the enemy jungler shows up, it is a 2v2, and with a weak laner you generally lose that encounter. So one of the successful parts of ganking a losing lane is not getting counter ganked. The only way to reliably do this is by having vision of the enemy jungler. This means that if you are trying to gank top lane (for example) to catch them up, your best opportunity would be when you see their jungler ganking another lane, or you have wards down that reveal the location of the enemy jungler.
This may get mentioned in a video about counter jungling perhaps, but tracking and being aware of the enemy junglers(and enemy teams) location can heavily influence what you have the freedom to do as a jungler. You can know that you can take their jungle, go for a dragon, gank a lane without fear of the counter gank from the enemy jungler, among other things.
