Lactic acid bacteria, temperature - delusion or truth?

Good day.
This is my first time on the forum, sorry if I created a topic in an inappropriate section, or such a topic has already been. For a week of viewing the forum, I did not find anything like it.
I just want to start the baking way. The ordered bread maker will arrive soon, I will try, but for now I am studying the theory.

Actually the most important question that interests me.
Many people write that lactic acid bacteria die in the leaven that is in the refrigerator.
Tell me, is there any evidence of this?
Why do I doubt ...
I make homemade yogurt in a yogurt maker from milk and special bacteria that I buy at the pharmacy (I will not give a link, if anyone is interested, you can google it, I use "CITO symbiform" and "CITO yogurt")
So, the instructions for these bacteria say that you need to store a bag of dry bacteria at a temperature of -18 - -20 "C, that is, in a deep freeze chamber. You need to store ready-made yogurt in the refrigerator at +2" C - +6 "FROM
I've always done this, never had any difficulty in killing bacteria
Why am I sure the bacteria were alive? I, like any resident of Ukraine, have common sense and do not have a lot of money))) that is, the "prescription" option - (1 bag of bacteria for $ 2 to dissolve in a liter of milk and make yogurt) is a little expensive. Therefore, I dissolve 1/8 of the bag in 120 ml of milk, prepare yogurt, which I simply use as a ferment for the next week (1 tbsp. L. Per 1 liter of milk). Well, it is clearly visible that the bacteria are alive, they like everything, no one dies. The taste and smell of the primary sourdough and the yoghurt prepared after is no different. The speed of cooking for both fresh bacteria and those that have been lying in the freezer for 3 months at -18 "C is the same.
So why is there an opinion that MK bacteria die at +5 "C?

Well, the second thought, although not in the topic of the topic, but all the same. IMHO it is much more convenient, faster and more stable to grow starter cultures in a yogurt maker A stable and comfortable temperature for bacteria, constantly maintained in the bowl of a yogurt maker will contribute to the strength and health of "tamagochik"

If the question is still relevant)))
I myself only understand the leaven, but I have not met the axiom you specified. On the contrary, I see a recommendation to STORE the starter cultures in refrigerators. And before use, "wake up" in the warmth.
I also put yogurt from 100 grams of the previous one. So there, so that there is no "stickiness", yoghurt is placed in warm milk. Apparently, it is desirable to "wake up" yogurt quickly.
In the refrigerator, even the breeding processes do not stop, they only slow down depending on the temperature. In the wine and on the high shelf, at a temperature of about 10C, only six times. Therefore, they write that, if the starter culture has not been used for a long time, it must be taken out of the refrigerator and fed. Yeast also does not live without MKB, since metabolic products of MKB are necessary for their vital activity.
Perhaps you just misunderstood, or caught on to one wrong message.

For your second idea, yogurt leaven. I do not pretend to be scientific, but so far I have read that the optimum temperature for yeast is about 25 degrees (although they often write about 30). The holding temperature of yogurt, and even more so at the bottom of many yogurt makers, is still higher than 30. Therefore, the angle on the refrigerator, if it is not in a draft, is quite suitable. Warm air goes up and plus side heat from the compressor.
I have not yet studied the issue of the influence of sunlight. On the one hand, it turns sour faster in the sun. On the other hand, a message flashed somewhere that it was not very useful for yeast.If any of the girls studied this issue, I will be grateful for the clarifications