My lay person take is they're using what is basically an EDF, you spin the impeller at high speeds sucking air in and ramming it out the back that is a lower di

My lay person take is they're using what is basically an EDF, you spin the impeller at high speeds sucking air in and ramming it out the back that is a lower diameter than the front. Surely many smaller engines would be safer than a couple of larger ones at those speeds. Also, maybe they found out it was more efficient to use many smaller ones.