I wouldn’t go that far, there is a plethora of games on itch.io that don’t go for a very fancy page presentation yet deliver in terms of in-game presentation and gameplay. As for this title…
I can’t be certain on whether it was or wasn’t stolen.
First impressions would leave me inclined that it is legitimate and made by the developer in question.
(Plus. When launching the game you do get the correct credits and everything.)
I may look around to see if there is more information available that disproves said impressions. Having said that, they’ve published two titles with similar aesthetic choices thus far which grants additional credibility.