you want to go back to my extended after reading this yes you do

Luchino is hinted to have narcissistic personality disorder (npd) and an eating disorder cannot be specified(ednos), this can be seen through his letters, deductions and quotes
npd:
"Astounding, isn't it? Yet that is the defect shared by most geniuses—arrogance." - 2026 Character day letter
"Before humans were fully evolved, we were no better than monkeys. Yet humans seem to have forgotten about this." - 2023 Deduction star quote
"Professor Luchino believes that humans evolved from monkeys. How ridiculous." - Yidhra's 6th character deduction - "Ignorance"
"If you think you understand the evolution and origin of mankind, you clearly know nothing about humanity." - Deduction star 2024 quote
"The great scholar, Luchino, is gone forever."
"I don't have the slightest interest in that day, much less in someone else's." - September 24th 2021 maintenance notice
ednos:
"A Comment: The report is very lacking. I must test its toxicity myself." - Professor's 4th character deduction - "Thirst for knowledge"
"Medical Record: Luchino Diruse's poisoning treatment records and risk report." - Professor's 6th character deduction - "Mania"
All of Evil reptilian's deductions hint that he stayed inside the lab for days experimenting on himself. This implies he might've not eaten as much.
"Unlike the Gila monster and the beaded lizard, the venom of this creature may change the world! I should speed up the experiments." - Evil reptilian's 10th character deduction - "Boundary"
Theres a lot more and I could go on but this is mostly the in canon evidence. Luchino being apathetic could also be Autism, but Luchino fits the NPD diagnosis criteria. His past is sadly, very unclear, so we don't know HOW he developed this hatred for humanity.
Evil reptilian can also be interpreted as a form of Luchino's "masked self" crumbling, as he gains the trait 'melancholic'. Professor is 'gentle' to fit the social standards and to be the great scholar he calls himself- So he won't be seen as "weak" or "less important to society.
Evil reptilian is a part of Luchino, but not entirely him at least. But, at the same time, if Reptilian!Luchino is a physical form, It could also mean he is ''looking down on others'' because he has achieved the "perfect" form.