Fan leaves are not only a plant's largest most efficient solar collectors they are also factories where sugars are produced and warehouses where food/energy is stored for use during hours of darkness. During hours of darkness plants allocate increased amounts of energy for growth and also for THC production (when in flower of course) over the amount of energy allocated for those function during hours of light. Everyone should want as much stored energy in their plants as possible so those functions can operate at their maximum efficiency.
Until fairly well along in flower plants will attempt to replace any lost healthy foliage. For each leaf or branch removed the plant will allocate energy to replace what was lost elsewhere on the plant. That of course means that when someone removes leaves or branches thinking by doing so they can redirect the plant's energy to be used the way they want it to be used what will actually happen is the plant will attempt to recover what was lost and other functions will be deprived of some energy.
Someone cannot force a plant to allocate it's energy the way the person wants it to be used.
People look at plants and say to themselves, well the plant has 'X' amount of energy and those darn big fan leaves have to use a lot of energy to remain alive so I will remove them and more of the 'X' amount of energy will then be used for bud growth. Well once you remove the leaves 'X' amount of energy then drops to 'P' amount of total energy to use because the plant cannot absorb and use as many light rays.
So now your total amount of energy is down from 'X' to 'P' and then thanks to removing the leaves the plant takes some of the remaining reduced amount of total energy, 'P', and allocates it for replacing the foliage that was removed leaving the rest of the plant to rely on only 'K' amount of energy.
The belief in trimming plants to force them to use their energy for bud growth is based in flawed logic and not in plant facts. At some point in time someone who knew nothing at all about plants connected dots that really do not connect and failed to see they did not create an accurate picture by connecting the wrong dots.
