I've had a similar message but I found out that it doesn't seem to have any effect on loading the file, so it can probably be ignored.

At Office Hours with Business and Marketing with Apple, I got that non-renewable subscriptions with free trials are not available directly from Apple subscriptions, but developers can certainly manage the free trials manually, blocking the app after it expires to prompt the user for a regular renewable subscription. This needs some backend support on the app side, to track if the user has already used the free trial or not.