To be fair, so did a lobotomy. I believe close attention should be paid to any unintended outcomes of a therapy that the patient themselves would no longer be able to identify due to the nature of the treatment itself.
Psilocybin is about the 180-degree opposite of a lobotomy, just from a purely mechanical perspective. And it certainly feels that way qualitatively as well.
Yes, although—within a specific range—mild "hormetic" stress or departure from baseline can lead to adaptive and beneficial effects in organic systems.
Hormesis is characterized by a biphasic dose-response: low-level exposures to stressors (toxins, temperature, exercise, dietary restriction, etc.) are those which stimulate adaptive beneficial responses, eg exercise, ischemic preconditioning (short bouts of reduced blood flow improving tissue resilience), and dietary energy restriction.
Rather than negating homeostasis, we can say that hormesis "refines" it: mild, intermittent stress can make us resilient through larger future perturbations.