I'm an amateur tree farmer/firewood dude so I'm sure many 'ole timers and "experts" will try and convince you I'm wrong (and maybe I am). But I've dealt with many hung up trees just like that, and most of them quite a bit bigger than the overgrown sapling shown in that first video. Instead of the complex wedge cut, plunge cut and then hinge cut, all I would do is to cut directly under the tree at chest height to allow the tree to fold under its own weight and collapse down from where I cut it. The main safety item is to know what's up in the tree and if any widowmakers are likely to come down on your head. A rotten core that can break on you in unexpected ways as you cut into the tree is another wild card. But then you'll almost always detect that as you're cutting through the tree (but you still have to watch for the rotten core in the big branches overhead). If the tree is canted at a sufficient lean angle, then usually this makes the widowmaker issue less risky (because few to no branches are directly overhead).
And another advantage of not doing the wedge cut and plunge cut before making your hinge cut is that as you proceed through the tree with the simple hinge cut, the tree will move more slowly and give you more time to observe cues as to when the tree wants to move and which way it's gonna go. You just have to ensure your hinge cut is aligned properly so that the tree folds the way you want it to. I just did a medium sized oak this way that was blown over by Irene. Its stump was pryed up out of the ground and the tree was laying on another big oak. After cutting the tree and winching it off its stump, I had to make 4 consecutive hinge cuts (as I described previously) before she would finally break loose from her sister tree holdin' her up. Each hinge cut was predictable and the tree moved slowly as she started telling me when she was ready to move (and not cutting in a big hurry either) - giving me plenty of time to step out of the way before each felling step. Still don't completely eliminate the widowmaker branch scenario, but a vigilant eye, a clear escape path and a good sense of your own mortality will usually keep you above ground.
My $0.02 anyway, don't spend it all in one place.