EH? The endosymbiotic theory has nothing to do with abiogenesis (the origin of life). Endosymbiotic theory postulates that eukaryotic organisms absorbed or were invaded by bacteria that developed a symbitoic (co-operative, like cows and their gut bacteria or ants and aphids) relationship with the host cell, later becoming organelles like mitochondria, or possibly that two types of bacteria acheived the same ends through a progressively closer symbiosis, one eventually absorbing the other.
This is one of two things, sheer ignorance and trying to sound with-it, or deliberately creating a strawman by maing it sound like endosymbiotic theory is a theory of abiogenesis.