These would be two completely independent transactions, involving agreements between you and two entities (whoever you exchange your MtG cards with and the Ohio Department of Revenue). There would be no connection whatsoever between the site where you arrange to sell your MtG cards and the site where your pay your taxes.
OhioCrypto.com is operated by the state of Ohio. When you register, the TOS says it is a contract between you and the Ohio Treasurer of State. To pay your taxes in Bitcoin through OhioCrypto.com, you do not first change them to USD via some third party. You present the Bitcoin payment information and your tax information, much the same way you would present your credit card information on a site that accepts credit cards.
OhioCrypto.com then uses BitPay to process the Bitcoin payment information, much the same way a credit card accepting site might use Authorize.Net or Braintree to process the credit card information, receiving eventually USD deposited to their account.
In your MtG hypothetical, in no sense would Ohio be accepting MtG cards. By the time they are involved, you are giving them USD. It would not make headlines because Ohio has no involvement.
With OhioCrypto.com, you are giving Ohio your Bitcoin payment information, and Ohio is dealing with having that payment information used to exchange your Bitcoins for USD. This makes headlines because Ohio is directly accepting Bitcoin payment information at a state run website.
Edit: updated to not imply Ohio holds Bitcoin, in response to tptacek's observation below.