I noticed that some global cards like VCC (Rewarble) are also offered when select a specific country, but I'm sure it didn't support my country when I last tried their service. What you should do is contact them and ask them to send you the official list of countries where the cards cannot be activated/used.
Actually, we use supported country list provided by gift card issuer for each brand. Just checked that brand and they are reporting for all listed countries, that's why listed as worldwide. We are considering to add "review" feature after purchase, maybe that way we can have user reviews that provide genuine user experience.