Essentials supports 4 hidden abilities, which is why it loads four individual abilities.
Essentials is built around the whole "dexdata" approach. species/abilities/forms and all that are loaded by opening the relevant data file, reading from the relevant section at the desired offset. This is an archaic data structure, but removing three string read points isn't going to make a difference. A real difference would be switching to a Hash-based data structure, like how item data is stored ($ItemData). This would actually have a noticeable impact on performance, unlike what is suggested here.