The camera is tracking his fancy remote/microphone. O0 Very nice video, very good teacher.
He doesn't go into many details, just what you need to do. That is good for beginners because it doesn't confuse them with technical explanations and encourages them not to give up. And it's also good for experienced people, because it tells you the straight problems, you should be able to fill in the gaps.
Note that he is talking about NPN power transistors, but nowadays most of switch mode power supplies use MOSFETs. Almost all MOSFETs have the protection diode included. Sometimes it's shown in their symbol, sometimes it's omitted, but it IS there and the same principle applies.
What is interesting is how permissive safety standards were. Not a word about discharging caps or any other precaution.
If you are interested in troubleshooting a SMPS, you should definitely check
this tutorial too. It's a way longer reading material, but a lot more detailed.