B.3. Highly restricted, fixated interests that are abnormal in intensity or focus (e.g., strong attachment to or preoccupation with unusual objects, excessively circumscribed or perseverative interests).
Excel is a highly structured environment that follows strict rules and procedures to generate outcomes, often sorting and making sense of "messy" inputs. Prime candidate for an ASD hobby/obsession.
Good question. I have known many people on the spectrum in my life including several close family members and loving spreadsheets is not something I would attribute to any of them.
Loving spreadsheets isn't something everyone with ASD loves, and I didn't mean to imply that, just the hyper-fixated interest (8 hours) on a something which I personally happen to love.