Truth be known much of what we know and what we think we know about the physiology of trees is not much more than speculation, aka, a guess. However if that guess repeats itself long enough in the same way then we assume it to be true. It is in this, and the time of year we repot trees, and the reason why we repot at this time of year are not as cut and dried as we would like to believe. We take comfort in our illusions as being something we can fall back on and depend on in all cases. When those cases do not cooperate we assume the asset cannot be dealt with at all, or only very carefully. This is the kind of scenario I used to get with Mugo Pines.
The issue of the bark is a good point that probably will not cry out for defenders on either side, it is simply something we can only guess at. In some cases we can duplicate it as has been pointed out, but we cannot define why it is so. It is like photosynthesis, where in we know how it works, or think we do, but we cannot make a test tube version that functions. It's why can't we make life?