You're confusing the retail, or B2C, buy now pay later industry...

You're confusing the retail, or B2C, buy now pay later industry with what Spenda is doing.
Spenda is providing supply chain finance, which is B2B. Their model is to improve working capital availability for retailers/wholesalers/primary producers through giving them access to funding which enables them to take advantage of early payment discounts on their supplier invoices.

If you consider a retailer that buys goods for $200k from a wholesaler and that wholesaler gives a 5% discount if the account is paid in 14 days, but the account is otherwise on 30 day terms. The retailer expects to sell all of the goods purchased in 60 days for $300k.

Retailer accesses Spenda supply chain finance at say 18%pa and uses $190k of their facility to pay the wholesaler within 14 days and gets a $10k discount. The retailer then repays the $190k facility in 46 days and pays $4,310 interest to Spenda. The retailer is then $5.690 better off having borrowed the $190k at 18%pa interest from Spenda.

If you consider the primary production opportunities where the producers have a supply contract with a major supermarket. The supermarket pays in 60 days from goods leaving the farm gate. The producer is owed $300k from the supermarket and has suppliers such as fuel, fertiliser, machinery maintenance, plumbing to pay totaling $120k, all of which give an early payment discount of 5% if invoices are paid within 14 days.

The primary producer borrows $114k at 18%pa from their Spenda facility to pay their suppliers for a total discount of $6,000. 76 days later (assume invoices are paid prior to produce leaving the farm gate) the producer repays the Spenda facility following getting paid by the supermarket and pays $4,273 interest to Spenda, and hence the $120k of inputs only cost $118,272.

You see, the retail BNPL model is targeted at people (retail consumers) who don't have the $500 - $2,000 to purchase something now, but are prepared to buy it now and pay it off over say 3 months in instalments. Those people then continue buying things they can't afford and eventually gives rise to bad debts for the BNPL provider. The Spenda model is providing liquidity to businesses who can afford it, as and when they need it and also giving those businesses the opportunity to save money by taking up early payment discounts.