One can spray a chelated iron solution on a tree exhibiting chlorosis and have the characteristic discoloration disappear fairly rapidly. The iron is incorporated into the foliar machinery that makes chlorophyl. However, chlorosis is indicative of the soil pH being too high, which means that additional energy is needed to pump the protons for the roots to extract other essential nutrients from the soil. This very real use of energy means the tree will not be as vigorous as it otherwise could be.
I serously doubt that those who espouse spraying liquid feeds, calling them foliar feeds, advise taking measures to assure the 'feed' doesn't also get into the soil/medium (one could use atomized sprays as another way to assure that the application is purely foliar). In other words, I am skeptical that the feeding is purely foliar. Instead it is a sprayed liquid feed that also goes on the leaves and maybe has some immediate benefits.
I think I have seen
Chalker-Scott's 'Foliar Feeding' article referenced in a post somewhere on BNut before. In my opinion it is a good, easily understood overview, well worth the time to read. If that is not enough, there is an abundance of scientific papers that can be found with the
help of Google Scholar.