Honestly I think it’s just a mistake no one caught. This store actually has some really good deals with these coupons most of the time. But it’s been weeks since I’ve taken this photo. And this “deal” is still going on! 
It isn’t exactly the same thing since the OP was talking about RTD but for anyone who is who prefers powder, I have found that mixing equal parts of huel and Soylent powder is really good, if you use the blender it isn’t gritty(straight huel is rather gritty in the blender), and you get the greater flavor verities of huel while keeping the powder price. The cleanup is also easier.