All it is doing is what a DAC does. Just dirt cheap.
Also you can not use an audio DAC for the purpose. The Digital TV signal from the TV is a 5.1 type. no compatibility with a two channel DAC.
You need a type of DAC used in a multi channel receiver, and a receiver which can convert it to a TWO Channel sort of RCA out. Plenty of them around. Find some used one with that particular feature. Which is Toslink in 5.1 Dolby THX with a two channel output available.
The device you linked to IS NO GOOD for TV to two channel.
The cheapest way is to buy a used cheap receiver and use it just to do the thing you want. Though you would have to make sure it can turn 5.1 from a Toslink into two channel BEFORE you buy it.
Older, PRE HDMI ones are more likey to be able to and be dirt cheap since they have no HDMI