Are you referring to the protocol setting in the Threat Prevention Profile editor?
Trying to extrapolate from the small screenshot, it looks like the setting that exists for the various Threat Prevention engines.
Indeed, it's possible to specify which protocols will be included in the scanning, but the default value for these profiles is to be "On" for HTTP/HTTPS. Most customers should not encounter this issue or have to touch this setting for HTTPS inspection to work.
Did you deactivate this in the past for your environment?
I'd like to better understand this case to make sure more customers don't encounter it.
Thanks!