You did not offend me at least. Given the stated goal, you could ask with a curious tone instead and avoid confusing you for someone rude/annoying. That said, you are right that technically, this isn't complicated. Sand physics like this is only a few lines of code. However, someone did mix concepts leading to a novel approach to an otherwise exhaustively cloned game. Tetris was huuuge in its day, and there are hundreds if not thousand commercial clones and variations. The interesting part to me is that novel combination. And, they went so far as to polish it as a game, share it for free, and all you have to do is click a couple of buttons.
So, if this inspires you to want to recreate it in canvas, have at it. It's probably a great exercise. The author can likely just build a target for the web and libGDX takes care of the rest. They might have to solve some build errors, figure out how to host it on itch, etc, and if they cannot be bothered, they don't owe anyone anything. Quite the opposite.
In summary, seemingly disregarding the novelty. Pointing out that it is simple, and that you (paraphrasing) cannot be bothered, is why I said that it could come across as entitled. In any case, have at it :)