I see this kind on mass in Calif. all the time. I put this statement in my reports. and move on.
Finding The inspector noted condition of an unknown fungi/mold located on section of the sub-structure framing. The owner/buyer should read the statement below for more information.
"This property was not inspected for the presence or absence of health related molds or fungi. by California law we are neither qualified, authorized or licensed to inspect for health related molds or fungi. If interested parties desire any information about the presence or absence of health related molds or fungi you should contact an industrial hygienist for further inspection."
****** Further Inspections Recommended ******

best