Terry Pratchett writes about this, how there is a difference between the sound of someone not being there and the sound of someone hiding and not making any noise.
He often writes about how things like bird song can be a type of silence and how a train that always passes at the same time every night, not passing at that time, can wake you up from its absence.
True silence is usually not an issue though, but there might be other reasons to record the silent room. Like getting the impulse response data, aligning the DC offset or getting the noise profile for noise reduction.
In other words: It's mostly used a reference rather than the explanation given in the post.
The different sounds of "silence" are the same as the different flavors of "water."
You're not hearing the silence, you're still hearing the absence of it caused by different things making little noises. (Or in some cases hallucinating)
You're not tasting the water but the non-water that's in the water.
Tap water tastes different from bottled water, and the bottled water from Brazil tastes different from the bottled water I had in Chile, which came from glaciers.
And yeah it's the minerals that give taste to the water, but I don't think you're supposed to drink completely distilled water in the first place.
I used to live in a pretty decently sized city. The quietest I ever experienced was in an old high-rise apartment after the power went out. I climbed up the seven or so flights of stairs because I needed to get into my unit to grab something, nearly all the residents of the building had vacated or were out of the building for one reason or another, so I was probably only one of about a dozen people inside during the power outage. I don't really know how many were still inside, but I'm sure it wasn't many.
Anyways, after I got into my unit I had to stop and listen for a minute. The windows were all closed and there was nothing. It was so quiet that I couldn't hear anything. At least to my ears that were numbed from the droning of the city. It was a marvelous experience. Normally you hear the buzzing of transformers, rumbles from steps and wheels and other things being moved around, the feint trumming of someone listening to music, and the constant mechanical whirr of the elevators working away. All of that was quiet. It was so still and calm.
I didn't experience that again until I moved into my current residence away from the city. Here I'm so used to the much quieter silence that I can hear the rush of air when the fans from the furnace turn on, I am acutely aware of the bubbling from the pet water fountain we have for our cat in the next room. Even the familiar pattering of my cats paws as he trots down the hallway.
There are lots of things dissolved in our water that give it "flavour", but the goal of all utilities is to minimize this as much as possible. Some water objectively tastes better than others, and a common segment of local drinking water conferences is a taste test. That said, for normal people usually the water they prefer is what their palette is used to. Someone who grew up drinking groundwater with very high alkalinity and pH will prefer that over surface water that is actually more "pure". Similarly, if you normally drink water from a private well that you don't add chlorine to, you likely dislike the taste of "city water".
The common offenders for bad tasting water are excessive chlorine and some specific organic compounds. Both of these flavours can be removed using a granular activated carbon filter (e.g., a Britta), but you can actually remove the chlorine by just letting your water sit in the fridge for a while.
A bit related a few months before me and my wife beame parents a friend of ours stayed by us for a few days with her very active toddler. I will never forget the moment they all left and I was chilling on my couch and it felt like negative sound. Like I would have to hear something just to break even.
After we got a reverse osmosis filter our water tasted like nothing. We had to get a remineralization filter to put minerals back into it. Now it tastes good.
This is a special kind of stupid. They're not recording silence, they're recording the ambient sound of the room. The entire point is that it's not silent, even if it is very quiet.