Sorry to drag this out! This one should be a positive, showUnsupportedRulesWarning, and default to true. The one on Audit should be unsupportedRulesWarningShown. So then we can have:

if (!axs.Audit.unsupportedRulesWarningShown /* we haven't shown the warning yet */ &&
    configuration.showUnsupportedRulesWarning /* the config is telling us to show the warning *) { ... }

Sorry if I put this in a confusing way before! Other than that, this is looking good apart from the minor commenting nit. Test looks great!