Yes. My understanding is that 1) You’d have to use abrasives, not steel files, to sharpen the hardened teeth and 2) Only the teeth are hardened. Maybe only the tips of the teeth, even. So even if you did apply some next-level sharpening skills and abrasives to a dull saw, you’d expect to wear through the hardened tooth tips and get into an unpredictable mismash of hardened, sort-of-hardened, and non-hardened metal. The re-sharpened saw wouldn’t be the same.
