These dual slots on many bags, most notably superdry. I doubt its design because its on so many different brands : r/whatisthisthing
Superdry Code Mtn Tarp Backpack White | Dressinn
Superdry Wheeled Holdall With Interchangeable Skateboard Wheels
Superdry Tarp Backpack Black | Dressinn
SWOON [Superdry white backpack] | Superdry bags, Bags, Backpacks
Single Wheel Bag - Nex-Gen Sports
Superdry Mesh Tarp Backpack - Dark Navy & Green BNWT | eBay
Extremely Durable Car Seat Travel Bag, Wheel or Backpack, Ballistics Nylon, Fully Padded, Water Resistant, Universal Size for Baby, Convertible and Booster Car Seats - Walmart.com