I like how they quickly glance over the fact that you need line of sight to connect and call that a good thing because people behind a wall cant steal your data.
Within the same room, it is possible to use a frequency of light that will reflect off of almost anything. I just got a window AC unit with a remote that defies physics. Like I can have a desk, and closed plantation shutters (slats and doors) in front of the receiver on the front of the unit, point the remote anywhere in the wrong direction and still activate the thing. It's just an IR LED transmitter setup. I've never seen one that is quite this powerful. It is uber cheapo general electric bottom of the consumer grade junk category too.
This is the NSA's wet dream tech. Anyone with line of sight could intercept the data stream.
For low datarates sure, but at high speeds the dispersion caused by light taking multiple paths will be unacceptable. The reason single node fiber is so thin is to make sure light can only travel along one path. If you want multi gigabit speeds, you will need a direct line of sight.
It absolutely is a good thing when security is concerned. WiFi is easy to snoop even if you're not physically in the room, if you know what you're doing. Sure there are encryption standards that are very good to tamp down on this. However, what's even better with LiFi is you must be physically in the room to intercept any transmissions that are being sent.
This is by design one of the largest advantages to LiFi. There are other practical uses as well, but it's not like LiFi is designed to explicitly replace WiFi.