Since getting into coffee, I've always been skeptical of the reason given for the importance of blooming. Most say it's to rid the grounds of CO2, that's all well and good and has always made sense. But, the reason given for WHY that is important or would make a difference was either not given or just accepted that escaping CO2 wouldn't allow water to penetrate the grounds. I'd also assume that it'd create some gas barrier around the grounds but generally that wasn't part of the WHY I'd heard.

Extraction, or at least my understanding, is much more than cell penetration, we also have erosion of the outer layers too. The erosion is influenced by many factors of course such as the speed at which water passes over it, the concentration difference of "clean" water vs the surrounding water that has some concentration of dissolved solids already in it, temperature, bean structure and density, grounds shape and so on.

With that said, I've been hearing more and more about channeling in pour over, usually it's the subject of espresso. There's more and more evidence that channeling has a significant impact on even extraction. I saw someone mention that blooming will help eliminate channeling. The escaping gasses create random pockets of varying densities in the bed thus making extraction and flow uneven. This makes much more sense and is probably the biggest factor as to why blooming makes a difference rather than cell penetration.

Perhaps I've previously only read "intro" explanations of the science behind it, but it's one of those basic concepts I felt people just accepted as truth without much data or a sound argument backing up the claims. Of course I could be entirely wrong, I'm not a chemist or anything like that, but thought I'd see what everyone thinks.