Something else to consider: there are some key factors that determine how much energy yeast and bacteria can generate: temperature, hydration, salinity, pH, food supply and metabolic pathway (aerobic or anaerobic). In the case of a young dough, generally speaking, food supply is always high and oxygen is always low, so the others are the ones we need to be concerned with.
There are three main functions for which yeast and bacteria use energy, homeostasis (the basic cellular processes to maintain a stable environment inside the cell – i.e. life), growth, and division. There is a hierarchy as to how energy is spent; first is homeostasis, and only if there is energy left over, is there growth, and only if there is still energy left over, is there division. As the external environment becomes less ideal (temp too high or low, pH too high or low, salinity too high, food too low, etc.) , the less efficient the cell becomes and the more energy must be devoted to homeostasis – simply staying alive – leaving less for growth and reproduction.
Extended periods of cold hit the yeast two ways – lower temp and lower pH. Both require the cell to devote more and more energy to homeostasis. 100% of the energy the cell has available comes from carbohydrate metabolism, and as previously discussed, this creates CO2. If you see signs of CO2 being produced, you have energy production. This does not mean you have significant division however, and if you’re not seeing much in the way of bubbles in the fridge, it’s not very likely that you have any meaningful division.
I bring this up because even if you’re right about weaker cells dying off, you probably don’t have reason to believe they are being replaced by stronger cells.