Shein is in reality just an aliexpress/baba wrapper, but they put huge amounts of effort into accurate sizing charts for their clothing, and their customer reviews system actively incentivises buyers to upload pictures of themselves wearing the purchased clothing. So as a potential buyer you can actually see the piece of clothing being worn by someone with a similar body shape than your own.

My impression of temu is they are trying to be as misleading as possible with their listings, and the value for money is absolutely terrible because of that: you think you are getting a 6' xmas tree for $20, but when it arrives it's 6".