That actually was the full game, not just a demo.
☆ NintendObs Weekly – Monday, July 29, 2019 – Sunday, August 4, 2019.
08.01.19
Nintendo Switch Online members, start practicing your swing! If you have a membership, you can play the Mario Tennis™ Aces game for free from 8/7 at 10 a.m. PT through 8/13 at 11:59 a.m. PT.
Be ready to play by pre-downloading, starting Aug. 1. Head to Nintendo eShop on your system, and look for the “Game Trials” notice on the game page.
You can even save 30% on the game (and keep your save data) if you purchase from 8/7 at 10 a.m. PT through 8/20 at 11:59 p.m. PT.
— Nintendo What’s New
Source: Nintendo.
At NintendObserver, the comments are on Discord.
Click on Community to learn more. 🙂
…
…Wanna play? Buy a Switch.
And if you’ve already got yours, click on Mario Tennis Aces for everything you need to know about the game. 😀