Etch is one of the best MKSC players in the world and is very active in the MK community (ranked in the Top 10 in non-SC and #2 in SC on the Player's Page). On his channel there are many videos of times even faster than the ones he has submitted to the site. He is a trusted player and has video proof for nearly every one of his times.
Also just because a TAS exists for a track doesn't mean it isn't beatable by a human player using a superior strategy. Just because he's not currently active on VGR doesn't mean his records that have clear video proof deserve to be removed from the site.