Founder here. COVID forced any retailer serious about staying in business to add online inventory. This was a prerequisite for curbside pickup. The world has changed a lot in the last 3 years and retailers are keeping this because they learned that 49% of consumers that go to the store to pickup a purchase add an additional unplanned purchase. Shoppers who try buy online pickup in store (BOPIS) tend to continue using it because of the speed, cost, control and convenience. It's free, it's on time, nothing breaks and an in store return is easy/convenient.

you're right that a retailer at least needs inventory in a database somewhere. Most do. The real issue is accuracy...