I'm running Norton 360 Premier v.22.5.2.15 on a Win7 x64 machine. I recently initiated a LiveChat support session (case# 24079117) because the Boot Time Protection setting in my Antivirus settings was grayed out. The technician used Norton Removal Tool to uninstall my product and then reinstalled it and the problem was fixed. I prefer the Boot Time Protection setting to be set to Aggressive and I discovered that as soon as I change the Boot Time Protection setting it grays out again. I tried turning off Tamper Protection to no avail. I've since uninstalled and reinstalled the product several times myself and the same thing happens every time. Notice at the bottom of the following image it says that restarting my computer will resolve this issue... it doesn't.
I don't know if this is working as intended but it necessitates uninstalling the product if I want to temporarily disable Auto-Protect for troubleshooting purposes.