Why does my writing score higher for AI when I'm writing fast vs when I'm writing carefully?

noticed something in my own testing that i’m trying to understand

i write blog content for clients and i’ve been running my own original drafts through detectors just to understand my baseline. what i’ve found: drafts i write quickly, stream of consciousness, first pass, score low for AI. drafts i’ve polished and edited carefully score higher.

this seems backwards to me. careful editing should make writing more human, not less. what’s happening mechanically?