Nothing questionable about that seller at all. Feedback looks solid.
Kind of misleading title lol. Aside from slightly low feedback I think everything looks totally fine
I actually recently purchased a sealed Bulbasaur/Squirtle Starter Deck from this seller. I ended overpaying a bit, but the guy was a pretty solid guy. The box was shipped incredibly well and the seller was very responsive! I wouldn’t consider them a questionable seller. I understand your concerns though - I tend to approach newer sellers with a similar degree of skepticism. I hope that helps a bit!
Good luck with your collecting!