Ingame help: caravan bonus style
Caravan bonus styles are not automatically documented. The only mention is in helpdata.txt and it for all rulesets says "immediate revenue in gold and science", that's why it is a bug. At least, we should say "in gold and/or science". Maybe we could auto-document all the table of trade route types.
Attached helpdata rewording at least makes it clear that all this depends on ruleset. There's no attempt for autogenerating the help to tell what the rules in the current ruleset actually are.