That is new, don't know if it was discussed elsewhere too. Quote from the prem shop, currently only as an option for the Obj 703 II:
If you’re unsatisfied with your experience in the Object 703 Version II within 14 days, we’ll refund your purchase!
Refunds are only available for 14 days after purchase. To receive your refund, visit our Player Support portal click on “Payments, Codes, and Premium Shop,” then click “I’d like a refund”, then “Create Ticket” and a Customer Service representative will respond shortly.
Not a bad move IMHO. We could have used it ages ago TBH.
Source: https://www.reddit.com/r/WorldofTanks/comments/i9uk2p/wg_testing_refundable_premium_shop_offers/