From Affirm’s help center https://helpcenter.affirm.com/s/article/affirm-credit-reporting-policy
From Klarna https://www.klarna.com/us/help/payments/what-happens-if-i-can-t-pay-on-time/
It is usually on a case-by-case basis which company will share what. What people forget is that if/when they don’t pay, then those loans can be sold to debt collectors which are much more likely to report to the credit bureaus.
What I thought was strange is that a couple days ago, CNBC ranked the best BNPL apps