Yes, It is TRUE that If Viola signs up to run Shopping ads but doesn’t post a refund policy on her website, she can’t run ads.

Explanation: When users buy from your site, they should be able to access your return and refund policy. Make sure that your return and refund policy is clear and easy to find. Even if you don’t offer returns or refunds, still state your policy explicitly.

Read more here: https://support.google.com/merchants/answer/6363310