First off, that link is NOT the 1.6 Android update. It is the HTC Hero ROM update. It's still using Android 1.5.
Second, the Sprint Hero uses a DIFFERENT ROM than the HTC Hero. DONT try to upgrade your Sprint Hero with that ROM. It wont work and can break your phone.
Third, I think the Sprint Hero should already have the 1.6 Android OS. CDMA wasn't available until 1.6 came out and since Sprint uses CDMA, I'd assume it's either Android 1.6, or 1.5 modified with parts of 1.6 by HTC.