>If robots instructions don't mention Applebot but do mention Googlebot, the Apple robot will follow Googlebot instructions. So if I set in my robots.txt to disallow all bots except Googlebot, Applebot will index anyway? I don't think I like that precedent.
I interpreted the sentence less literally and more like "in absence of rule, default to GoogleBot ones"
So if you put a wildcard rule forbidding access and a specific one allowing access to GoogleBot, AppleBot will honour the wildcard one.
That's how I would have coded it anyway: parse the rule for current agent string, if no rule applies, run it again with GoogleBot one before assuming that website does not contain restrictions.