Just as an update for anyone looking for more info, alicorns do drop a "full" energy refill, although its one point below yor max energy.
What i mean is it takes into account how much energy you have the moment you collect, and what your max is. For example, if my max is 40 and i have 1 energy which i use to collect, it gives me 40-1= 39 energy. So its not really really a full energy refill, since it doesnt give 40, and one should definitely collect from the alicorn on 1 energy and mo more, because youd be wasting alicorn drop if you had 5 or 10 energy for example.