Otis is noted to be an odd case in story, given that he was basically the first test subject for the process. Robot-Otis is clearly Otis's Soul+Memory Aethers, so (Proto?)Endless-Otis can safely be assumed to be a copy of Otis's Memory Aether data pushed into some blank Aether rather than the original after being essentially surgically separated like later Endless.

As for Erenville and his mother, he's just being hopeful even though the whole process of making an Endless involves an accelerated version of the natural process of things where the Soul Aether is reborn while the Memory Aether is lost, outside of deeply traumatic events that end up "scarring" the Soul Aether like witnessing an apocalypse.