You can buy them both from Gary Larson’s company.
That’s not unique. These token showings allow production companies to sell videos and DVDs as theatrically released movies rather than “direct-to-video”, which is preferable for marketing and/or legal reasons.
I would assume in some cases, companies would do it for award-nomination purposes as well: I believe to be eligible for an Academy Award, a film has to have had a run in a theater in either New York and/or Los Angeles during a certain time period.