Validation will stay pending until your account is eligible to receive a payout. We have to pay a processing fee for the validation so we delay it until we actually know you need to be paid.
This should be written directly on the Tax Information account settings page, https://itch.io/user/settings/seller/tax-information:
Your tax information is on file and your account is ready to accept payments. Your tax information must pass validation before you can collect your earnings through a payout. Validation is a one-time process that will happen when you open your first payout request from your dashboard.