I was reading that but couldn't see anywhere that it was something included. It does say "By default, ActionPolicy::Base adds one alias: alias_rule :new?, to: :create?." Is that the only alias available by default? If I just wanted to define update? in my policies I would have to make an alias myself?

Here are the defaults included into ActionPolicy::Base: https://github.com/palkan/action_policy/blob/master/lib/action_policy/policy/defaults.rb

The default_rule :manage? configuration says that all rules not specified explicitly should be handled by the manage? rule.
So, if you defined def manage?, it would be used for update?, edit?, destroy?, etc. (unless you define them explicitly).