It’s a tiny thumbnail and both look almost identical. In all the times I visited the Huel website, I never once thought maybe I should stop what I was gonna do to take out my magnifying glass and spot any minor differences between this plain black t-shirt and the plain black t-shirt they’ve been giving away for years 
Huel could have displayed 2 or 3 different clothing products in the thumbnail (like they already do with other product ranges), or even just mentioned in the short description “beanies, jeans and jackets” or something. The image mockup itself is also highly generic and doesn’t attract attention or embody the brand at all.
IMO it makes no sense for a company who’s been giving away free plain black t-shirts for years, to represent their entire clothing brand that consists of beanies, jeans, jackets, joggers, caps, etc with only a small thumbnail image of a plain black t-shirt that looks almost identical to the free one that everyone already knows and has, with no mention of other products, and no marketing of those products anywhere on the website or in the delivery packages.